Well, I was supposed to be visiting Shap and a few of the sites round that way on Sunday, but weather and a bad cold got the better of me! So I stayed in bed and did a bit of reading on the subject instead...
I found this quite interesting:
"When Stukeley saw 'the great Celtic temple' in 1725 many of the stones had already been broken up. 'It proceeds northwards [from Kemp Howe] to the town [Shap], which intercepts the continuation of it, and was the occasion of its ruin; for many of the stones are put under the foundations of houses and walls... or blown up with gunpowder'. Mistaking the northern 'avenue' and the single row to its west for the remains of an interrupted extension to the southern avenue he said that the line curved westwards, claimed it was serpentine, saw the immense Goggleby Stone, but was prevented from drafting what would have been an informative plan by rain that has so often accompanied attempts to make surveys of avenues. A later draft, made by Thomas Routh in 1743, has been lost."
From Carnac to Callanish, Aubrey Burl (page 48)
So it would seem that there was only ever one plan of the site put together, as Burl doesn't mention one anywhere else, and that was lost! Oh well... There is a sketch dated 1775 on the same page in Burl's book, but it doesn't really shed much light on the layout of the place.
Interesting to note that it was the weather that stopped Stukeley from drafting his plan, some things never change, eh?!