MG ZR 120 Stepspeed gearbox issue

[will.booth]

Hi guys and gals, i am new to the site so please bare with me.
I have a 2004 reg mg zr 1.8 stepspeed which i brought brand new. Had my fair share of issues with the car but it is a great car, i love it to bits. I have started to refurbish the car as i havent driven it for nearly 4 years as it needed a new drive plate so instead of fixing it i brought a new car as i did alot of driving for work. The cars tatty now but i will never part from it and wish to restore it.
I recently took it to a auto gearbox specialist that i have used since i got the car as its had two new boxes and 3 new plates now.
Got car bk 2 days ago, althought the garage shown me the parts that they replaced the car still revs up whilst in motion (D)or going through the tiptronic(M), it will rev up and as the revs decrease where it gets to the point where it should be and it shudders, sometime with great force almost stalling nearly killing me and anyone driving behind me. The garage said CVT boxes dont like being stood driving it should cure it, been driving it since friday the box feels looser and like its freeing up but still on occassions will do this. Does anyone have any experience of simular symptoms? Id love some advise. If anyone can help me with my pride and joy id be very greatful.

[JOHNDQ]

The CVT box is a nightmare tbh i really cant think of any that i know of that are right after being repaired and parts are not easy to find. Last one we dealt with had new chain and valve block but still had the high rev problem Where abouts are you based

[will.booth]

I'm based in leicestershire.