There was guy called Nathan Millward who rode an aussie postie bike from sydney to london! he wrote a book on it and its quite interesting and judging from the people he met id say there are plenty of people to do this route across europe and asia. You can get bus tours or many people use motorbikes and do it them selfs. Google Nathan millward, he has a website and it might have infromation useful to you. hope this helps.
If you do go, have fun
Ha I met Nathan in Manali in India! I also met two French girls that had walked from the stans down to Nepal. I later had emails from them after they had continued back out into China then down to Thailand all on foot! It's amazing what some people are out there doing.