I'm really not too "up" on prices of Quarter Horses in the UK so this will just be a slightly educated guess. Purely on the information you have given, I would say he hasn't done very much so a minimum of £4,000, but likely £6,000 because he is palomino.
right oh - yep I should have put a bit more detail.
Brill in traffic, very mature for age and is relaxed when schooling, have started showing and is good on fun rides, not done very much. Snaffle mouth, confidence giver, can be a handleful but that is due to age, easy to tack, with farrier etc...
Well that wouldn't change anything for me price-wise. With QH's most buyers are looking for the bloodlines (at least they are over here). What breeding does he have? He doesn't look like a Foundation Bred horse, but that doesn't mean that he doesn't have pretty decent breeding.
Yep your right, he does have pretty good breeding though. His dad has won quite a bit and he runs under the Joe Peeps blood line. Both his parents are USA quarter horses.
His mother is a bay and his father is a palomino.
Joe Peeps? Sorry I've never heard of that line - am guessing that is a mish-mash of one of the Joe lines and the Doc lines? If you go back to the foundation stallions on his pedigree then you'll see the lines, or use allbreed to help you if you can't get that far back.