Harrifer,
I live in Kent, so not too far from you.
I use Timberline in Tonbridge, Kent. They are a god source of supply but not the only one.
Good backing materials available in the UK are hickory (can get it from Timberline but sort through the stack for a good bit) or bamboo (try doing a search for Bamboom, they are not too far from you.
Belly materials are many. Ipe is good. You can get this from decking suppliers, or hardwood suppliers like Morgan's in Rochester, Kent. You can also buy Massuranduba from them which is almost as good but be wary of checks within the wood. Timberline sell a number of woods such as lemonwood, pau amarello, purpleheart etc. I don't think prpleheart is really up to a heavy longbow though. Pau Amarello seems quite good.
there are many glues you can use. I like resorcinol, sold as Extraphen here (try Axminster power tools). Many bowyers have had good results with titebond3, but I haven't really experiemented with it myself.
Why not pop over to my club near Rochester (Bridgewoods Field Archery Club) for a shoot and a chat? We are NFAS and quite friendly. My friend Peter and I both make bows and would answer any questions you have.
Email me at
markdesignhill@aol.com if you want to chat further.
Mark in England