Zen not the cheapest but their service is excellent
Since it's normal to kick ISP's when they're down, I thought I'd just add my 0.02 Euros worth and comment positively on their service. I know this is going against the grain but hey ho...
My view is that shit happens to all ISP's, it's what they do when it goes wrong that you pay for. When I have had to call Zen I have managed to get through to somebody quickly (no 30 mins hanging on the telephone), they have been very knowledgeable and were very happy to go straight from "have you rebooted the router" to a sensible technical conversation without going through every stupid option on their crib sheet, they have called me back when they said they would and generally I'm as pleased with their service as I can be.
I pay far more than the cheapest providers but then again I get a good service from them with UK people who really do understand what they are talking about, are happy to have a Smoothwall firewall in the way and were genuinely interested in solving my problem.