Well, just to cap this thread off, i managed to find an independent willing to sell me a new ETM without the core charge, £225 delivered.
Also got a local independent to program up the new ETM for £40 (after i fitted it on their forecort to save an additional £65!!)
After about 20 or so miles the car is now running very well, initially it was a bit odd and not easy to drive, must have been re-learning the new throttle positions etc.
But yes, now it is fine and dandy.
Plus point is its doing an additional 5 mpg too.