If there are any particular issues you have with the onboard catering, then perhaps we can suggest some self-catering options to work with.

If the menu is not appealing then what protein and vegetable options do you like?

As one of the shortcomings of BA's on-board catering is the single tray service, this might be a tricky one to substitute.

Self catering will obvious be limited to cold food options so maybe focus on salads, cheese plates. Plane Food is pretty good here.

The Pret, Boots, Starbucks etc suggestions don't sound very appealing to me but the key here is keeping the food fresh without refrigeration