I've just been on the phone to QB carbon - they won't be going to Ally Pally Superbike show this year, but will still do a deal if we want to order a number of seat units.
As with most things, the price depends on the quantity......
As I recall their normal price was £150 for fibreglass and £250 for carbon.
If anyone is interested in joining forces then drop me a mail (not U2U as I can't seem to access it?).
Cheers
Paul