Freecycle has come up trumps many times so far. I think I've managed to get 3 A1200s in various conditions, one with a nice accelerator in it and a couple C64s. No sifting through shit like at car boots just post the question asking then turn up at the persons house.
About 30 games with one of them, all boxed in good condition. Managed to get £80 after fees on ebay