HELP AND ADVICE PLEASE

[WRS4]

Ok I have a strange issue here I hope someone can advise me about. I was actually going to post in a few months to say my car is for sale and it still is after this situation has been resolved but lets sort this matter first, as for selling her it is a hard decision but I am 50yrs old this year, ive had my fun with her and its time too move on, so if anyone is looking to buy a rs4 this year then keep me in mind as mine has had a lot of works undertaken too her be it mechanical and also mods done by MRC, anyway moving on...

So 15 months ago I had a full gear box rebuild and repair and a new clutch and flywheel fitted, apparently warranty is only 12 months but surely after spending 4k id expect far longer than 15 months use IF THIS IS THE ISSUE OF COURSE ?

So basically I have been having no issues with the car, on my way home I did a tight right turn and the car felt like it had slipped into neutral, I checked and it was still in gear ? so I just took it out of gear and put it back into gear and all was well and I thought nothing of it and continued home about a mile. When I got home again I had to tightly turn right in order to reverse into my drive, I put her in reverse and reversed up, as I had to straighten her up I went into 1st gear and as I let the clutch out the car wouldn't move ? I then put her back in reverse and again nothing ?

I have a clutch pedal and still feels like its under tension / pressure as it should, goes into all gears nicely and smoothly as if nothing is wrong, when not in gear I can put the clutch up and down and no sounds, but once in gear if I lift my foot off the clutch pedal the car doesn't move, revs go very slightly up and I get a sort of spinning / grinding noise from under the car ?

Any ideas lads ? and if related to the work I have previously had done should they not fix it as a good will gesture as 4k for 15 months sounds pretty crap to me, as I say I am only assuming not saying its related at all.