Any suggestions?

I had a brand new pattern cat fail an MOT with less than 10miles on it!

Watch on Ebay, I put the exhaust manifold downpipes and catalytic convertor from my "spares" car on Ebay and it was there for months before I managed to sell it for £35 including postage. It was certainly a genuine cat but possibly not original due to looking less than 21 years old, the downpipes were literally like new. I took the other cat to the scrapyard alongside the remnants of the bodyshell and got exactly the same £35 but no postage involved. My experience with dismantling the two cars is that there is virtually no demand for the mechanical bits but seats, trim, good subframes  etc   sell very well.
 

Thanks to all who've contributed to this thread. The MOT was done today and it failed miserably! Various wear 'n' tear stuff - Major - lower front arm and wiper blades. Advisories, rear discs, track rod ends and rear tyres. On emissions the CO - 0.80% on the first then 0.71% on the second idle. I could hear the car being put through its paces and he certainly gave it every opportunity to get it ducks in order, but it wasn't to be. HC passed easily, as did the lambda. So, the plan is after advice from my friendly local Austin Healey/MG restorer is retest at his preferred location, aftermarket cat fitted, get a pass on that and get other items done. Then sell and get me a BGT! If there's no CO pass, another otherwise perfectly good usable TF will be gone off the road. 🤷
Cheers,
M.

Good luck. I really hope you can pass one way or another

Sound as though it just needs a bit of TLC to get it through the test, don't give up on it.