In reply to carrot_boy: FWIW im confident there would be demand (indoor venues generally seem to be swamped, certainly liverpool and both the manchester walls are) but i guess, subject to your aspirations and finances, it would be worthwhile starting small with the option to increase size.
some people have mentioned PlasPower, unfortunately its limited in terms of size and whats on offer:
- the space used for bouldering isnt maximised
- there appears to be no set problems
- it looked like both the overhanging board and traverse wall hadnt been changed in ages
- the traverse wall is "cushioned" by use of stones and not mats and there is little distance between you and the adjacent wall / window ie potential for awkward falls
- there is no fingerboard or campus board
- atmosphere is lacking with holds and tools sitting around the place which added to the generally unfinished / DIY feel of the place
- OK for occasional training but not a venue many people would regularly frequent i guess