Bit of an update on this. After speaking to others about this, it has come to light that I might not have to replace the complete IMRC.
There's a transistor on the pcb which has been known to fail through overheating and I reckon that as the said transistor uses the IMRC body as a heat sink, it won't get sufficient cooling whilst the IMRC is bolted metal to metal to a hot engine!(dumb Ford!!

)
So I figured as it costs next to nothing to replace the transistor if you are good at soldering, I'm going to have a pop at this, and relocate the imrc to a nice cool part of the engine bay whilst i'm at it. This should cure it for good I hope.
I'll report back with my findings.