Has anyone tried out 18185
www.18185.co.uk (sister company of 1899 and 18866) and used them for calls to 0870 numbers? According to the website, their weekday (& evening) rate for such calls is 4ppm (plus 4p connection charge). This is just over half the rate charged by most of the other 'cheap' providers and, as far as I know, the best rate since 3U realised what they were doing... Unless, of course, anyone knows a better rate?
Interestingly, their 0845 rate is not so competitive at 3ppm - in fact, it works out more expensive than BT!