This is a good deal for this bulb, currently 40 quid on Amazon. There is a newer version of the bulb out and that is smaller and uses slightly less electric but it's 54 quid. I have one already and it's really good. Just ordered two more from Vesternet who seem to have a good rep but never used them previously. Charged me £3.95 delivery for both bulbs.
Yeah it's expensive for a bulb but cheap for this kind.