Good report. Do you realize that your bus fare from LGW to LHR was about a third of your airfare? kind of insane!

Just buy a one way next time, for 12 quid. That is a fantastic fare. In Europe though the cheap fares are you buy it, you eat it. If you can't use the ticket, TUFFF!!!
As for Boots being cheaper airside, because it is like Duty Free. Though the dear Europeans went off and abolished Duty Free within Europe(INCREDIBLY STUPID MOVE, HAS COST THEM MILLIONS $$$ ), you were technically on a domestic flight, so the stores eat the tax, which is not bad. Though more of a deal if you fly out of the EU, hence, long live Switzerland, smart enough to stay out of all that and they retained their sovereignty.
Anyway, for BM, they can be good, and I actually do like their sandwhiches, but they are nasty on the rules. Can only check in 2 hours before, with a need to be onboard 30 minutes before, that is not alot of time for lounges, Duty Free, and playing around

). They are strict with carry on rules and all that BS, hence, I stick with BA, which isn't as anal but they can have their moments. Try to get their people to smile, that is fun. I had one crew to Madrid, all sourpuses(i.e. not one smile) and they are terrible with foreign languages, not a single word of Spanish. ugh...
As for seating, some planes do have decent legroom, while there are a couple with charter style seating, absolute hell!).
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MD
AA PLT,1 MLN Miles+
Hilton Gold
Sheraton Gold