Hi,
F&M do a picnic to go IIRC ( as do Plane Food)
In December I did CW to DXB ( daytime flight). I bought a small coolbag with me and bought a sushi pack from Itsu. That served as a starter to compliment the CW starter and also kept half to have with the second light meal prior to landing in DXB
Regards
TBS
PS : The F&M picnics can be preorderd via the heathrow airport website. Details here
https://heathrow.orderwithgrab.com/22321 ( from £16 to £28) The Caviar plate goes from £90 to £320