No surprises. The prices look like they have based them on what easyJet charges, the drinks are almost identical and the food prices are in the ballpark (some higher, some lower). I don't know how these compare to what M&S charges instore, but am guessing the store prices are a bit lower, which is what I would expect.
The only difference to easyJet is that you can't pay with cash on BA, but you can pay with Avios, the exchange rate will be interesting.
Full on head to head LCC competition between BA and U2 from LGW, that should be interesting.