Thanks Jeremy that's really helpful. It's a relief to start seeing some options - I was originally concerned that I had a unique fault. I just heard from Cayman Autos of Dorking who seem to fully understand the problem, and can do the repairs, so I'll talk to them next. Alan

 

Not uncommon, but now expensive to replace. It's not too difficult but is time consuming - I've just done my second one!. For info, Porsche published a TSB for the earlier model (similar parts and procedure); see here:

http://www.pcarworkshop.com/index.ph...C_Parts_Guides

and download No 15.