Buying a bike in Japan and driving to England

[CaptainTim]

Ok, I've been looking all over the site and still have some questions. I'm planning on buying a Dirtbike in Japan and travelling across Asia and Europe (China, Vietnam, Cambodia, Thailand, Malaysia, Laos, Tibet, Nepal, China, shipping to Turkey, Greece, Italy, France, Spain, England). Here are my remaining areas of concern:
1) Buying a bike in a Japan and getting a Carnet: it seems like this is done in lots of countries and I assume Japan is no different; does anyone know about the plausibility of buying a bike in Japan and registering for a Carnet
2) Driving in China: is it possible to ferry a bike into China and be allowed to drive it?
3) Tibet: I've heard it's possible to drive into Tibet without dealing with the government paperwork hassles? Is this doable? If so what route would be good from China to Tibet to Nepal (sorry, I know this should be in the Routes forum)
4) Is a Carnet really needed for Nepal, India, Turkey, Greece and Italy?
5) Is getting foriegn damage and theft insurance for the bike worthwhile?
6) If shipping from India to Turkey is there any special paperwork needed?

This is my first Bike trip, and first trip to all of these countries, so any advice would be very much appreciated.
Thanks,
Tim