Comparing a BA flight with a Ryanair flight is not comparing like with like. They operate out of different airports at different times. If I lived in Windsor I'm not going to buy a Ryanair flight from Stansted because it's £30 cheaper. The cost and stress of getting there add up to way more than £30.

And expecting BA to price the same as FR or U2 is unrealistic, even if you just look at airport costs. BA pays £28 to LHR for every departing passenger, whereas LGW charge around £12. So instantly you've got a £16 price difference based on jut the airport you use. I expect Stansted is much cheaper

For shorthaul my main priorities are airport location and schedule, as long as price difference is within £50-100. I would barely consider the other factors like free food, it's only a 2-3hour flight