Ok, all things considered, I have changed my PEK-LHR seat to 63A. Reason being that I do think 62K might have been cold due to the door and I hate trying to sleep and being cold, so taking T8's advice here. I also get the feeling that 62K won't have the side bins and I do like them.
However, should 64K become free between now & my departure date, then I will change it again if I can but happy that I've got 64K booked for my return flight in May.