Do you reckon that the time i've planned for the below 'overland' sections of my trip realistic?
Delhi - Calcutta (via Agra & Varanasi) 2 1/2 weeks
Kuala Lumpar - Bangkok (via some of the islands and a possible short trip to Chiang Mai) 3 1/2 weeks
Shanghai - Beijing (via Xian and great wall) 3 1/2 weeks
I only have experience with India, but I would say your schedule is fine. Of course it depends on how slow you like to take things and in how much detail, but you can always get a train from anywhere you are at to Calcutta and be there in less than 24 hours.
Thanks for the reply Alty!
It's good that you said that as I've booked my flights now.
We've actually left about 3 1/2 weeks for India as we really don't want to just rush!
The big question mark at the mo is travelling from Hong Kong to Beijing via Guilin (we're not going from Shanghai anymore) - but we will have about 4 weeks to do this and have been told that should be fine.