Food
You should be fine leaving from Europe since the catering is from there. Leaving Beijing is a different story - the food will be barely edible even for the Chinese option. Cabin crew speak basic English only so you need to be slow and patient with them.

IFE
You should be fine with your own entertainment options, but check whether the aircraft you are flying has power plugs.

Delays
Beijing is often subject to air traffic flow restrictions even in good weather. Arriving shouldn't be a big issue but leaving Beijing may be. But perhaps they might prioritize a London departure to prevent paying off a big sum for a nasty delay due to EU regulations. This is likely the most frustrating part as ground staff in Beijing are not too good with English so any arrangements for cancellations will likely be messy and frustrating.