Finally all sorted!! Put new seals on the injectors and very carefully reassembled it all back together. Fired the old girl up and it's purring like a kitten again. All fault codes have been cleared and it took itself out of restricted performance mode, so pleased at last.
Took it on a 10 mile test drive, very easy on the throttle, and all good, temp good and stayed in the middle, heaters worked well and no complaints at all.

Thanks again for the help and advice.