Thank you all for your advice. On the back of it I have decided to focus on one country this trip. Since my initial plan was China, this is the country I have decided upon.
My itinerary is a bit rough atm - I'm still undecided about whether Xi'an is worth the time/cost (Terracotta Army being my main attraction). I want to plan excursions, using Beijing as my base to avoid moving around too much. Not sure how feasible this is.
Fri 30th August LHR to Shanghai arrive 31st
1 - Shanghai
2 - Shanghai
3 - Shanghai
4 - Internal flight to Xi'an
5 - Xi'an
6 - Internal flight to Beijing
7 - Beijing
8 - Beijing
9 - Beijing
10 - Beijing
11 - Beijing
12 - Beijing
13 - September Leaves Beijing
Specific recommendations for China, in addition to Beijing, depend on what your prime interests are: history? natural scenery? villages/old towns?
All of the above. Any advice is gratefully appreciated.