Got to the bottom of this! It was a faulty EGR, although it was clean and looked ok I tried a new one and the car is spot on!
You can use this to check your EGR, I found it very useful as my old egr the resistance values where all out:
http://www.partinfo.co.uk/files/Pierburg-SI0085-EGR Valve Sticking.pdf
Problem is, I was un-plugging sensors in the engine bay with the engine running and it wasn't activating any MIL lights! Turns out the electrical architecture on these engines is fairly primitive and a-lot of it is open loop so the ECU can't tell when some things up the guff anyway! The -40 reading was due to the car not having the capacity to relay IAT back to the OBD reader, so the OBD reader was seeing a certain voltage and default reading -40!
If the diagnostics system was better I would have saved time and money but hey ho its a learning curve!
Next time I clean the EGR I'll take some pictures and do a write up, its really easy to get to and I'm sure anyone with a few tools could do it!
Cars back on form now tho and I bought some wheels to celebrate 
