Hi Simon,
I have just bought a long 1st and dropped 5th type-9 from BGH geartech in Cranbrook, Kent for £570ish. I went down to the company to pick it up and was very impressed with the work they do there, they certainly seem to know what they are doing.
Unfortunately I havn't fitted it yet so I don't know how good it is or how easy it will be to do (I am converting 4 speed to 5 speed), probably a job for this winter.
Some more info on them can be found here:- http://hometown.aol.com/dvandrews/bghpage.htm
Hope this helps