Is this a reasonable price?  Been told £30-£70 from a local Vaux dealer dependant on what, if any 'tweaks' may be needed.  Was trying to get it in an independant which is cheaper but running out of days to get it sorted out as need the car next saturday for holiday an MOT is already run out.

Looking at getting a diagnostic done to verify the cause of high emissions on the MOT, suspecting the cat and replacing it would likely solve for MOT purposes.  Obviously this will push the overall cost up slightly if it is the cat, but should ensure I fix the problem, rather than changing cat and finding I have a problem somewhere else = more cost.

I would of looked at trying to get it done by one of the guys here, but time and travel are against me as I am not the luckiest guy in the world and if I drove it any distance I just know something would happen and I would get nailed for not having a valid MOT!