Hello Phil, Shame there is no noise track on here lots of problems would be easy to solve. Now there's an idea. Threads with sound.
To try to understand the noise grinding grumble.
Where you changing gear quickly or steady, was it worse if you changed gear quickly, and better if you paused slightly as you selected.
Was it gears grating as they meshed, this would be a weak synchromesh on that one set of gears. 4th
If that is the case its got a limited life. very approx. 5000 to 10000miles before the change will get really noisy, then the gear will jump out when coasting off power and eventually jump out when on power. If that all makes sense?
Normally 2nd and 3rd gears are the first to wear the synchromesh out.
Second hand gearbox £200 but about 6 to 8 hours labour to fit it.
Sorry I cant be sure without the car here.
regards mark