Yes, London can be a pain (and potentially very expensive) unless you get a good transatlantic deal, the timings are right, and you know what you're doing with transfers/hotels.
I'd disagree about the online check-in with Ryanair, though. In practice online check-in doesn't change anything, except that they can charge you more if you haven't got the extra piece of paper with you. It would be great if you could just walk into the airport, avoid the desks altogether and go straight through security to the gate, but you can't. In effect you're paying £6 to save them printing a sheet of paper (or £30+ if you forget to print it yourself!).
I missed my flight back from Valladolid in March, which I'd already 'checked-in' for. As far as I know it didn't lead to a security alert at the airport!
Buen Camino!