Great idea, Gav! And needless to say, all three are excellent photos.
As the photos stand, no. 2 is the best for a jigsaw because there are sufficient contrasts to help with the refit.
Nos. 1 and 3 have a lot of cloudless sky, which would make a jigsaw extremely difficult. This could of course be solved by means of some cropping, but I believe that the standard jigsaw proportions would need to be maintained, which means that cropping the top would also lead to some (unwanted) cropping at the sides.
Alan is the expert -- he has now prepared two very successful jigsaws for publication!