The RSCDS claims Wilson is the source for this dance; I have my doubts. He certainly wrote dances with this name, but if his work is the source, it has been so modified by the interpretation that almost nothing of the original is left. The second "single figure" seems the closest, but even it only shares half of the first figure...

Wilson, on page 37, writes:

SINGLE FIGURE (Each strain repeated)
Hands 3 round on the ladies side hands 3 round on the gent: side   lead down the middle up again & set to the top Cu:  

OR THUS The 1^st lady meets & turns the 2^d. gent: the 1^st. gent: meet & turn the 2^d lady   lead down the middle up again & allemande  

DOUBLE FIGURE (Tune played twice thro' with repeats)
Set & change sides with 2^d. Cu: set & back again   1^st lady meets and turns the 3^d. gent: the 1^st. gent: meets & turns the 3^d. lady   promenade 3 Cu:   & whole poussette  

Wilson's music consists of 2 four bar strains, both repeated. Wilson's dance is not set to strathspey time.

Wilson spells his title "The Haughs of Cromdale" rather than "The Haughs O' Cromdale".

RSCDS Book 8 says this was "collected in Moray."

Wilson, on page 54, writes:

SINGLE FIGURE 1^st strain repeated 2^d. played straight thro' & D.C.
Swing with right hands round 2^d. Cu: then with left   lead down the middle up again & right & left with top Cu:

OR THUS Set & hands across with 2^d. Cu: set & back again   lead down the middle up again & set to the top Cu:

DOUBLE FIGURE (Tune played played twice thro as marked)
The 1^st. Cu: cast off at the same the 3^d. Cu: set & lead up then the 3^d. Cu: cast off & the 1^st. Cu: set & lead up to places   cross over 1 Cu: half figure round the 3^d. Cu: set contrary corners   lead thro the bottom hal pou^e.

Wilson usually gives multiple figures for each tune, the RSCDS appears to be following the DOUBLE FIGURE.

Wilson defines most of his figures in his An Analysis of Country Dancing.
Except that the first figure is not explicitly defined.
Cross over 1 Cu: is not defined either, but Cross over 2 Cu: may be found on page 22 and means "cross go below 2s, cross again, go below 3s". (so presumably crossing 1 Cu: means stopping below 2s.)
half figure may be found on page 54 and means "the active lady loops around the man below ending in her partner's place, as the active man loops the woman below ending in his partner's place. set contrary corners may be found on pages 55-57 and means "move to 1st corner and set, pass partner right moving to 2nd corner, set, return to places the easiest way". Wilson does not show the corners setting back.
lead thro the bottom is half of through bottom and top on page 23 and means "the active couple take hands, lead down below the bottom, drop hands, and cast up to their own places.
half poussette not defined. A full poussette is defined on page 53 going once and a half around the neighbor couple. But half of once and a half doesn't make sense here. Dancers have already progressed so going a full circle is probably what he wants to happen.

The crib diagram attributes to Wilson, 1825. According to The Regency Dance site Wilson didn't publish anything in 1825. The Scottish Country Dance Database also gives a date of publication as 1825, but gives no devisor.

Quite a number of people published dances named I'll gang nae mair to yon town but none matches the RSCDS figure: Thomas Wilson, 1809, Hime, 1810, Chivers, 1821, Chivers, 1821 (different work), J.P. Boulogne, 1827, R. Hill, 1830.

On page 24 of book 10, Campbell writes:

The 1^st. & 2^d. Cu Poussette quite round to their own places Lead down the middle up again hands 4 round at bottom Right & Left at top.

The music consists of an eight bar strain and a sixteen bar strain. I assume it is intended to be played AAB.

Campbell spells the dance "Miss Ogleves Fancy".

According to the the Regency Dance site Campbell did publish a dance with this name. Whether the figure matches I cannot check.

In Wilson's A Companion to the Ball Room, 1816, (page 33) he published "My Only Joe & Deary O". Wilson writes:

SINGLE FIGURE (Tune played straight thro')
Hey on your own sides   lead down the middle up again & allemande  

OR THUS Swing with right hands round 2^d. Cu: right & left with 3^d. Cu:   lead thro the top & turn your partner  

DOUBLE FIGURE (Each strain repeated)
The 3 ladies lead round the 3 gentⁿ.   the 3 gentⁿ lead round the 3 ladies   promenade 3 Cu:   & whole poussette  

Wilson provides 2 eight bar strains, presumable played as reels not strathspeys.

Wilson defines most of his figures in his An Analysis of Country Dancing, 3rd Edition.

1. the three Gentlemen lead round the three Ladies is defined on page 16 and means "The gentlemen take hands, and, with M1 leading, dance clockwise around the ladies and back to places. As they do that the ladies take hands, advance into the middle, pause, and fall back."
2. the three Ladies lead round the three Gentlemen is defined on page 16 and means "The ladies take hands, and, with L1 leading, dance counter-clockwise around the gentlemen and back to places. As they do that the gentlemen take hands, advance into the middle, pause, and fall back."
3. promenade 3 Cu: is defined on page 18 and means that all three couples take promenade hold and, with the 1s leading, travel in a counter-clockwise elipse around and back to places.
4. whole poussette is defined on page 15 and means: "top two couples join hands with partner, circle, counter-clockwise, one and a half times around the other couple to change places with them."
   Note: this is unlike a normal English Poussette as the couples travel once and a half around each other rather than once. And is quite different from the Scottish Poussette.

Wilson spells the title "Auld Langsyne".

SINGLE FIGURE (Each strain repeated)
The 3 ladies join hands & the 3 gent: join hands set & lead thro' set & back again   set & change places with the 2^d. Cu: set & allemande  
OR THUS Set & half right & left with 2^d. Cu: set & back again   & whole poussette  
DOUBLE FIGURE (Tune played twice thro' with repeats)
Cross over 2 Cu: set   half figure on your own sides allemande at top   whole poussette   set contrary corners  

Wilson usually gives multiple figures for each tune, the RSCDS appears to be following the DOUBLE FIGURE.

Wilson defines all his figures in his An Analysis of Country Dancing.
Cross over 2 Cu: may be found on page 22 and means "cross go below 2s, cross again, go below 3s".
half figure on your own sides may be found on page 67 and means "weave around the dancers on your own side, move between the couple above, then outside the next couple, finishing at top."
allemande may be found on page 7 and appears to mean a gypsy. This is an unusual meaning for "allemande", but, as best as I can understand, that is what Wilson describes.
poussette may be found on page 53 and means "top two couples join hands with partner, circle, counter-clockwise, one and a half times around the other couple to change places with them.
set contrary corners may be found on pages 55-57 and means "move to 1st corner and set, pass partner right moving to 2nd corner, set, return to places the easiest way". Wilson does not show the corners setting back.

SINGLE FIGURE (Each strain repeated)
Hands 3 round on the ladies side hands 3 round on the gent: side   lead down the middle up again & set to the top Cu:  

OR THUS Set & change places with 2^d. Cu: set & back again   lead down the middle up again & cast round the top Cu:  

DOUBLE FIGURE (Tune played twice thro' with repeats)
Set & half right & left with 2^d. Cu: set & back again   promenade 3 Cu:   whole poussette   whole figure round contrary corners  

The music consists of two 4 bar strains. Probably played as a reel rather than a strathspey.

The RSCDS is interpretting Wilson's DOUBLE FIGURE

Wilson defines most of his figures in his An Analysis of Country Dancing, 3rd Edition.

1. Set, and half right and left may be found on page 50 Everyone sets in his or her place (he doesn't say whether this is to partner, neighbor or corner) then L1+M2 change by left, then M1+L2 change by right.
2. promenade 3 Cu: is defined on page 18 and means that all three couples take promenade hold and, with the 1s leading, travel in a counter-clockwise elipse around and back to places.
3. whole poussette is defined on page 15 and means: "top two couples join hands with partner, circle, counter-clockwise, one and a half times around the other couple to change places with them."
   Note: this is unlike a normal English Poussette as the couples travel once and a half around each other rather than once. And is quite different from the Scottish Poussette.
4. whole figure contrary corners is defined on page 104. Rather awkwardly, Wilson provides two different (contradictory) directions. In the first "the 1s cross down, W1 in front of M1, W1 around M3, M1 around W3, then cross up, W1 around W2, M1 around M2, and return home". In the second the "1s cross up, W1 around M2, M1 around W2, then cross down W1 around W3, M1 around M3, and return home.