It may not work for you but I live fairly close to Heathrow. I noticed (and judging by the amount of English on the plane I wasn't the only one) that if you were prepared to change flights in either Frankfurt or Munich and you booked at the right time, return flights were £150 all in and it was Saturday out and Saturday return at reasonable times. I have to admit that I have not found the same for 2012 yet but it's still a bit early.
Yes emjay, I found the same as late as January this year.
Like you say, people do take this option to save costs and it may even work out more convenient (I saw B'ham flights via Paris) for £148 which would have been fine.
Ian, I think one has to be creative. For example a friend of mine flies into Austria on a nice cheap Easy Jet flight or equivalent and then hires a car and drives to the Czech republic where he goes skiing. He claims he saves a fortune against direct flights