In the case of stabilised wood, chances are, it will probably have come from the US even if you buy it in the UK or Europe.
http://www.stabilizedwood.com/
However, if you are just starting out I wouldn't recommend splashing out on expensive handle material like that. The same goes for the hidden bolts available from places like
www.texasknife.com.
You can make a very good knife using natural wood from the people already listed, or somewhere that sells turnery timber (Craft Supplies, Timberline in Tonbridge, Axminster, Tilgear...lots of places). Be aware that some tropical wood sold for turning is not fully seasoned and can change shape after you cut it. If there are any good gunsmiths around your way you could see if they have any off cuts of walnut. I have had several pieces that way and it is often stunning wood, and very well seasoned.
For holding it together, use 1/8th inch diameter brass rod that can be found in nearly any model shop (drill with 3.2mm drill). Aim to use at least four pins and you won't have any worries about the slabs coming off.
There might be someone on BB who can sell you some vulcanised fiber liner, but it isn't absolutely necessary that you use it. Nice, but not worth getting hung up on.
One last thing...knife making can be habit forming for some people, in which case it can become much more expensive than buying a custom knife to start with
Good luck
