In reply to Mlewis:
I've got a lot of doubts about how useful/profitable a guidebook for an entire country as big as the UK or France or Spain would be if it only had a handful of crags in it but assuming it is something people would want/buy, I think maybe:
Gogarth
Pembroke
Scottish mountain crag (pick from Shelterstone, Dubh Loch, Ben Nevis N face, Coire Lagan, Etive slabs or Carnmore)
2 scottish sea cliffs (this would just be so hard to narrow down, Mingulay and Pabay might be contenders but who would ever go there without getting a guide showing every route? Hoy and Screaming geo (+other geos) are superb but they don't get any traffic and both are long ferry trips to get to. Reiff and Sheigra and Neist Point are all popular and great quality but they are also rather shorter pitches... a bit of a lack of scale. Ellen's Geo is fantastic but it's also very new, it could be considered a pretty brave pic.)
A couple of grit crags (not my area of expertise).
Kilnsey or Malam for the limestone sport stuff (not my area of expertise).
Something in the Lakes (not my area of expertise).
Sharpnose/Bosigran
.....
Ok, I've thunk about it a bit more, I don't think you want 25 crags, If you create a book where the whole of Scotland has like 5 crags in it, I just can't see how it could be useful. I think you want more like 100 crags across the UK with 10 to 30 routes per crag - that fits in a largish book and gives people some options with route and crag picking.
I did once start looking at making a UK guidebook aimed at visiting climbers but never got beyond a bit of research (i.e. climbing!). It might be helpful to take every crag in the UK and start narrowing down from there, that means you don't miss anything too obvious out. There are only a few thousand crags in the UK and a huge, huge number of them you could discount instantly for being grotty quarries or isolated as hell slabs with just a couple of routes. I think before you knew it a list would start to form quite organically.
Unrelatedly, when did jimtitt turn into such a troll? I swear he used to make interesting and useful posts but this is like the third thread I've read with obvious trolling... Did his account get hacked?