I found and attended the ACCU conference in Oxford last year. I found it quite affordable at 695 GBP, and it was hands down the best conference I've been to. The speakers were great, the topics were interesting (programming languages, testing, developer processes, etc), the size of the conference was just right. The speakers were fun and knowledgeable, and had no qualms about joining the masses. In fact at one event the speakers and the masses were joined up in an networking activity. It was awesome. The wifi was flaky but is something I could deal with no problem. I've often wondered why there isn't a developer conference like this here in the states?