In reply to Petar Samkov:
I've done it overland returning from Kathmandu to London via Nepal, Tibet, China, Kyrgyzstan, Kazakhstan, Tajikistan, Afghanistan, Uzbekistan, Turkmenistan, across the Caspian Sea to Azerbaijan, Georgia, Armenia, Turkey, Bulgaria,Croatia, Hungary, Slovakia, Austria, Germany, France, UK. We took 9 months.
I'd recommend Jet Airways if you want something faster and cheaper.