Again a little off topic for the general subject matter of this site but as it's closely related to my business I think it deserves some attention.
I've jusy come back from reading Aral's blog and he's very annoyed with Vodafone as well as Abbey National Business, two companies that have given him nothing but grief - something I can very much relate to.
Aral pointed out that he didn't want others to call the 0870 number when canceling a Vodafone contract but use email instead. Well here's another option: check out www.saynoto0870.com, a site which lists geographical phone numbers for hundreds of UK companies. You can then ring those numbers rather than the expensive 0870 number. The site is a bit heavily laden with ads but still worth checking out.

You can combine this with the service from 1899.com, a company that offers a pre-dial number to make cheap calls. In fact so cheap that it almost looks like a scam: 0p/min (that's FREE!) for all UK landline calls and dirt cheap rates to most other countries.
I frequently call the USA and Germany and I can do that at 1p/minute to both landline and mobiles. All that's needed is a credit card registration at 1899.com and that's it. No need to change your phone provider, simply pre-dial 1899 and you're done.

I have used their services for over a year now and my phone bills have come down dramatically. I've changed to the cheapest BT line rental package and then make all my calls via 1899.com. They are actually cheaper than Skype's skypeout feature, cheaper than Vonage (who really are a scam for UK users when compared to the US prices) and cheaper than TalkTalk. Give 1899 a try, you won't regret it.