Been on the look out for a new HDD upgrade for my ps3 and this little beauty has popped up many times and this is the same price as ebuyer.com delivered it all depends on who you prefer. I suppose if one runs out then order from the other.
Here's the link for ebuyer - http://www.ebuyer.com/product/136790
£37.94 + £2.58 super saver p&p = £40.52
The most popular choice among ps3 users for the upgrade just now and there is a very well detailed forum on avforums.com here - http://www.avforums.com/forums/ps3/823886-hdd-upgrade-what-you-need-know.html
Next cheapest, i can find, delivered is play.com @ £41.99