Hi All and thanks for the advice.
I have optically centred the scope(what a painful experience). Taken everything off cleaned and checked. No arrestor pin. Nothing pushing it up as far as i could see.
I am not using the MTC connect mount but two standard low mounts. I think McDemon is correct as they are side by side i don't think a shim will make any significant difference, particularly bearing in mind how far in the up direction the scope is adjusted already.
For the time being i have moved to high mounts and when the weather(its p**sing it down here as i write this) is better will see what the situation is then. I have also put a wanted up for MTC connect mounts to see if that makes any difference.
Once again thanks for all your help.