In reply to zimpara:
Just a few more suggestions to add to the mix:
Everything below VS on Bochclwyd Buttress
The brilliant Terrace Wall Variant on Tryfan isn't a wall because it's all in balance, but it feels like a wall – especially if you do it in big boots ...
The top pitch of Little Chamonix (V Diff) on Shepherd's is certainly a wall - vertical, if not slightly overhanging - but covered in the most absurdly big jugs you'll find anywhere.
Appian Way on Pillar.
I haven't done it, but January Jigsaw on the Buachaille must surely fit the bill. Monstrously exposed.
If you get to Skye, Naismith’s Route ""v diff"" on the Basteir Tooth is very steep and outrageously exposed.
But the king, below VS, is probably still Tophet Wall - which has to be one of the best routes just below VS in Britain. V exposed at the top.
... Actually, about on a par with Main Wall on Cyrn Las, which I wouldn't quite describe as a wall. A v clever wandering route up an extremely steep and exposed buttress.
Post edited at 22:26