Used to be with them back in 56k dial-up days, but left after they "lost" my account for three months in a row. These days I wouldn't touch them with a barge pole. They consistently rate as one of the lowest on thinkbroadband's comparisons, even when compared with AOL and BT Broadband.
This is a comparison of AOL, BT Broadband, o2, PlusNet, Tiscali and Zen. The results speak for themselves.
I'm glad to see that there are people out there who are having a good experience with them, but after having seen so many of my clients have issues and problems with them, and seeing those problems run on for long periods of time, I have no inclination to use them and I would never, ever recommend them. Even PlusNet had problems with them when they were reselling some Tiscali broadband services.
I can only get about 7mb (or what ever the speed thingy is) down our phone line
The link you posted shows similar results for AOL & Tiscali.
AOL are charging me £17.99/month for 2mb
Post Office are charging me £10.72/month for line rental (+free evening & weekend calls)
Tiscali are offering 8mb speed, line rental & the same calls package for £14.99/month.
Seems like a no-brainer to me.