Steven,
Best of luck on this project. The two most prolific suppliers of exotics in the UK that I am aware of have already been mentioned, kirk at exotic hardwoods UK ltd at chapel en le frith, and Bob smith at timberline (website exotic hardwoods.co.uk!! Guess that's why kirk called his business UK ltd?) in tonbridge. Since the demise of angels in Germany a couple of years ago these are the two main importers. Kirk tends to have more woods originating from the Americas whereas Bob has a fairly world wide collection. However, Bob used to be a Lutheran and started his business due to an inability to get consistent wood. I don't know much about tonewoods but the consistency of the wood and density is paramount. An example is ebony, Makassar ebony, diospyros celebica, has a density of 66lbs a cubic foot and provides excellent treble tone reproduction whereas Asian striped ebony has a density of only 63lbs, below the threshold for good tonal reproduction and the reason that Asian striped never got the price of good makassar ebony. There is debate about the segregation of the species but the patterns are quite distinct. However the debate is that the tree is the same but the differing density and weight is a result of differing growing conditions of the same tree. Different websites disagree.
Anyway, a good tone wood is going to be expensive and I have no idea what wood you need for which instrument, but I am sure that if you are on the way to Pompey down the a3 Bob smith would be delighted to help you. Chap called Andy fellows in gosport used to sell 3mm instrument sets in a variety of woods, you might end up with a good set by googling tone woods. Sorry if any of this has already been said earlier, haven't had a chance to read it through thoroughly.