update - electrician has had a good look at it (ex TVR guy) done a few tests here and there, does come up with a processor fault so pretty much confirms PCM bit wonky.
PCM ordered should be here tuesday, Stage 1 and 2 will be updated by Ford onto PCM, hopefully car will start so that will be a good test. Awaiting to hear from MT to see if car can be driven locally for a few weeks as a test using stage 2 on the Stage 3 engine mods. I know it can be driven as one was driven to Mountune with the inlet for Stage 3 already on. So my options are to test it or just low load it straight to Essex when the PCM and Stage 2 are on.
Looking like £2,000 best part of this will be.
This is quite rare, am aware of one RS PCM failure. In order to apply Stage 3, PCM is split open, so if not resealed or anything gets in could be the cause, will never know.