Thought I would update on my GT engine.
I spoke to Ned at AutoLusso and he was very helpful, though as I am in Scotland it is a bit far to his repair centre.
I had a couple of pointers in this forum to try McLennans in Edinburgh and so I got my car over to them, as my local were still looking for a new engine!
Stewart at McLennans has been very helpful and the prognosis appears to be that every single rocker has broken, but all the valves appear to be ok. So although my GT engine is a newer one it still didn't totally break!
The initial problem does seem to be a water pump failure causing the timing belt to go. So everyone make sure you change these after 4 years at the latest!!