My fuel pressure was shooting off the gauge (over 10 bar) under load. After changing the fuel pressure regulator it turned out to be a faulty fuel pressure sender.
It's a VDO part - stock number 360 081 029 010 (10 Bar - Single terminal - Earth via thread - M10x1 tapered thread).
Merlin Motorsport had them in stock for £32.34 plus VAT and £7 (next day before 1pm) shipping - Quite a good deal and a nice bloke on the phone I have to say.
They are on 01249 782 101 if you need them or http://www.merlinmotorsport.co.uk
Thanks also have to go to Julian Godfrey for talking through the possibilities and offering to send me his for testing.
Bit of a blurry image...