I've played musical ISPs like many of the guys in this thread, nildram, plusnet..., bt and sky. Been with virgin for a few years now and have no regrets.
I'm so jealous. So you've had five ISPs? In the US, you're extremely fortunate to have more than two broadband options in any given area, and most of the time one of those is going to be DSL. Where I live, I can go with Verizon Fios, Cox Cable, or probably some Verizon DSL service and that's it. Other places might add in ATT UVerse but that's pretty much it.