Hi all,
An update on this. Its been a while as I haven't had time to fit the injectors since getting them back.
I sent the injectors off for cleaning and the temp sensor for checking.
The temp sensor IS over reading. That and the boost gauge are knackered so time to replace.
Now that the injectors are back in and cleaned I am not having the problem that I was having on cruise so there was clearly an issue with them sticking randomly.
I gave the car a run today and all seemed fine (no boiling hot red turbo) but I haven't driven it like I'm on a track as I have recently been in trouble with the police so have to stop driving like an idiot for a while.
Next step is to change the gearbox, brake disks and pads (cracking). Replace boost and temp sensor and then look into what mapping is required.