Its a strange problem and I'm not sure what the cause is, but what I've done is gone to a version before smoothing. What I've found is I can smooth out the model, but I can't change the subdivision back to 0 then back to 2 again as this seems to also cause the problem.

So I'm going to finish it off without any smoothing and then smooth at the end. I can't even smooth and then undo without causing problems.

Thanks for the Info