When I moved to the Lakes I had a full sus. After a very short time I bought a HT cos it was far less maintenance and far more fun. I've yet to find anything in the Lakes I can't ride on it and its coped fine with plenty of all-day rides.
Try as many bikes as possible, see what you like. There's a whole WORLD of full sus out there everything from "XC/enduro" (typically 100mm travel) to "trail" (approx 120-140mm travel) to "freeride" (140-160mm) and loads of marketing speak, technobabble, facts and figures. There's plenty of good shops in the Lakes though: Keswick MTB, Wheelbase, Evans (Kendal), Biketreks (Ambleside), most of the shops will have test or demo bikes, KMB and Wheelbase often organise demo days where you can try several bikes for free on proper rides. Get onto their websites, find out when the next one is. Try hiring bikes at trail centres or next time you're off on a biking holiday look around beforehand for any local bike shops and book a test ride or a demo bike. If you're going further afield, companies like AQR out in the Pyrenees have a demo fleet of Cotic Hemlocks. Try mates bikes or ask the opinions of the local riders - KMB runs night rides every Tuesday from the Pedlar, join in with them and see what people are riding, what they recommend.
Above all, take your time with it, no point buying a bike and finding out its not what you want. Might be worthwhile waiting til the end of 09 when the bikes are discounted, you can use the time til then to work out what you want/need. In the meantime buy some bigger tyres for your Merlin - I'd go with 2.3" or so for the Lakes!