Coldicote: You may be interested in this. The Which? Recommended Broadband Suppliers are (in order): Zen Internet, Be, Eclipse, Utility Warehouse, O2, Greenbee (John Lewis) and Plusnet. As you can see, O2 is the only one of the "big boys".
The four they recommend you avoid are TalkTalk, Supanet, Orange and AOL Internet.
I'm with Greenbee - not the cheapest, but very good or excellent in all other aspects. Their service is actually supplied by Plusnet, whose own product is rated as "very good value". Hope this is of use.