For far its looks like UKOnline then.
My main choices were UKOnline and Zen, I was a little sceptical of UKOnline though because it is half the price of Zen for exactly the same service, and is a 12month contract. Ideally i would like to avoid a commitment that long as i have had some shocking ISP's in the past.
As for 24Mb ADSL-2, apparently that will be available on my exchange from February so would kind of screw with the 12month UKOnline commitment? Although saying that i'm sure it will be ludicrously expensive when it comes out, and i very rarely max out my 2Mb as it is