I used Tesco dial up 24/7 for a couple years at 12.50/mth, never had a problem with them, very reliable. I now have 0.5meg broadband from Plusnet at 14.99/mth (1meg/mth download limit), also great so far, plenty of scope for browsing and small downloads. Additional one off connection charge though.
I was with Free 24/7 up to last May when I ordered ADSL so they have been around for a while. I found I got what I paid for meaning, that sometimes it took a few attempts to get a connection in the evening but once connected it was fine. Not sure if there's a 1 hour cut off though, you'd have to check. I stayed with them for around 2 years so they weren't that bad.
Something to bear in mind, you don't get email services but if you have an existing account with another PayGo provider or a webmail account you may not need this.
They are a subsiduary of V21, you may of heard of them?
I use Onetel for my telephone provider and my ISP. Cost are £13.95 per month for free UK phone calls (or something like that) and £9.99 per month for "after hours" internet. i.e Dialling up the internet costs me nothing. If you go down this road be careful because some 0870, 0845 numbers are termed `non-geographic` and you pay 10P per min. on them. All that said my phone bill each month is very acceptable. Hope this helps. After hours is from 6PM to 8AM weekdays and 6PM Friday to 8AM Monday. sorry for the omission