Ok total bill 1700 pounds including a cosmetic fix (which was the S on the back becoming loose and needing replacement). I can deal with that, although it's a nice ski holiday equivalent - ouch!
No I don't have the sports shifter but am considering getting one as I am about the track the car this year and I find the travel a little long. I only get notchiness in 1st and I suspect you're right - ambient temperature issue. After the repair the OPC filled the engine with exactly the right amount of oil and still no notchiness.
The car works basically fine now although there seems a little hesitation occasionally. Let's see how it goes. It is still quick - I warmed oil up to 90 degress plus and took it for a blast down my local section of motorway - nice little twitch on the back whilst accelerating down / round the corner of a slipway and I had forgotten the performance / sound - nice reminder & good fun! No-one else on that piece of road of course - well after midnight.
<<Nerd alert>>
If you are interested, the problem was a malfunctioning tappet solenoid. This component controls the two piece tappets (there is an inner core and outer ring) which engage with either of the two profiles of the cam (inner cam lobe or outer two lobes - outer lobes engage with ring, inner lobe engages with core - but not at the same time as these are effectively different cams). It does this via oil pressure variation and because it wasn't working the wrong pieces of the tappets were engaging with the wrong part of the cam - probably at the wrong time - resulting in misfiring etc. Apparently the bracket holding the tappet solenoid into the engine commonly breaks resulting in the same symptoms.
Lucky I didn't drive it too far or it could have got really nasty.
Happy to post pictures from another site showing the bits if anyone is interested.
Apparently this is quite a common issue along with ignition coil failure so if you have bad misfiring - really, really rough idling - and stalling (rather than just a bit of rough performance until the engine warms up which is a coil issue) - then you might want to mention checking the tappet solenoid to your OPC or specialist. I suggest this because my OPC took the valve cover off one bank of the engine (and I think removed the camshaft) before finding the solenoid was the issue. I've just got to hope they put it back together properly...
<<Nerd alert over>> 
