2005 facelift Cooper, A new exhaust was fitted from the cat back and afterwards a harshness / vibration could be felt at about 2300rpm, all the mountings have been renewed and the exhaust has been changed again. Both top engine mountings have been renewed recently but still have the problem.

What type of exhaust was fitted?

Euro carparts after market standard exhaust system. The first had the centre mounting bracket welded in the wrong position and was exchanged.

Pattern exhausts are renowned for bad fitment, specially when not done right. Does it sound like that could be hitting the car or heat shield underneath?
Have you had a look under the car?

Have looked under car and the exhaust does not seem to be touching heat shields, I was thinking may be the centre mountings are under to much pressure or perhaps the flexi is on the way out ?

Jump back under there and wobble the exhaust side to side yourself, see if you can hear anything knocking.

I would be looking at the exhaust causing the issue. Do you know what make the Euros part is, was it Bosal? We have seen loads of issue with aftermarket exhausts and clamps causing similar noise at certain revs. If it wasn't there before but is now that is most likely.

Otherwise it could be the CAT. We have seen them break up causing noises. Comes as part of the manifold.

Thanks for the advice, after yet another set of mountings needed fitting decided time to change exhaust, Klarius after market system now on and vibration seems to of gone