Thanks all. Useful info.
An opportunity has come up to compare v the BA WT+ product; I'm sure some things will be better and others not.
But food is something I can do something about in the LGW N terminal if I'm possibly looking at a PE weak point there.
Given GGL doesn't guarantee me first dibs in BA F anymore I'm unnaturally reticent on food options, even though I am rarely fussy unless it comes to egg!

VS transatlantic in Y, ex-LHR, I've always got my first choice.
BA (and AA) do have pre-order ex-LHR in F & J & W, and for extra in Y.