Keep an eye out for offers in the likes of Tesco, Sainsburys, B&Q etc in the North.
There are subsidies in place in the UK for these bulbs and there are regularly offers like 10 for a fiver
I have a few of these bulbs, but am very wary of them. A pregnant woman should never be in the same room as a broken one. And there will be long term effects, when these things start piling up in rubbish dumps over the next few years. Mercury is pretty bad for you! http://ironwhirlygig.wordpress.com/2008/03/21/cfls-good-and-bad-for-the-environment/
I bought 5 Phillips CFL bulbs in Sainsburys in Newry around a month ago, they were 99p each or 5 for 50p!
I thought the price was wrong so just bought 5 of them but when I checked receipt they were just 10p each. There is a subsidy for the UK supermarkets to sell them.