It’s true the party system distorts first past the post. It’s also true, I think, that AV gives smaller parties a better chance, provided they do enjoy substantial support, because people don’t have to be sure they’d win to risk voting for them. But like first past the post, the single-member constituencies (a strength, in some ways, I think) do still allow the political parties to hold a lot of sway over individual candidates. Neither system is the best or the worst in this respect, though.
Would AV avoid the swing you describe? I’m not sure. What’s the evidence from places like Australia? I’d have thought only a more proportional system would avoid this, but I need to read more about it. While I think proportionality is generally a plus factor, it’s not a deal-breaker for me.
Anyway, thanks for your support. I’ll do my bit not to let you down!