Hi, have a problem with my car I think

While I was decelerating on my engine today (so loosing speed without using breaks) I thought I heard a grinding noise from my transmission... however it was short and then dissapeared so I thought perhaps I immagined it and didn't thought about it anymore... Car still drives smooth.

However, when I got home I parked it on my driveway in reverse, like I always do... but as soon as I had the car in reverse, and letted the clutch go, I heard this rattling / grinding noise again

Anybody know what the problem could be? It's a A32 model, from 1995, 180k miles on it, 5 speed manual, 3 litre engine. Please fellow org'ers... help... Bit worried here