After finding a small damp patch on the garage floor I've traced it to the steering rack return pipe at the drivers side front where pipe goes into the rack.
From what I can tell the leak is due to the flange on the pipe being burst at the bottom ie nothing on the lower half of pipe to mate against recess on the steering rack.
Is this a complete new pipe required, I came across this part code and wasn't sure if it was a repair kit 999 230 543 40
Wasz found these guys and I regret not using them. The pipes from OPC are over £400 *each*. Get both pipes and replace them at the same time to avoid the labour costs in the future. Its not a huge job for a good indy
http://www.powersteeringstore.co.uk/porsche-911-power-steering-rack-pipes-(1998-2005)
Not sure about the DIY bit - I wouldnt want to do it myself due to the "unique" steering rack bits that apparently can be quite fragile if you mess it up. Not sure if anyone has done these DIY who can comment?