Hi meggles,
Have a look at this site - it's one of the best in the UK for this ...
http://www.thinkbroadband.com/look over in the forums section, and there's a forum called ISP Unhappiness, all the ISP's are listed and from all the posts you can get a good idea of the kinds of problems associated with each one.
There's also a 'good ISPs' or 'recommended ISP's section too -
The problem with the 'Free Broadband' offers is that they were oversubscribed and deluged with interest and they couldnt 'keep up' with demand. Things have gotten better but they (talktalk, the orange offer and others etc) are still semi strugglin with demand.
Look 'very' carefully at the small print, the will be caps and limitations - if you're usage falls within them, no problem, but if not, it's best to go for a 'proper' paid for service.
Personally, I prefer 'best of breed' - the best/most suitable ISP service, the best/most suitable phone provider, best/most suitable tv package etc. Sure overall it costs a bit more and I get 3 bills - but it means I can switch any one of them when a better deal comes around! currently I'm investigating 'Be Broadband' as they provide unlimited up to 24 MB internet for £24.99/month which is £3 less I'm paying now for only 2MB/month.
Overall, check carefully all the terms and conditions and clasues and offers within the package before signing up...
hope this helps!!
Cheers! DtM! West London & Slough UK!