Hi Jake,
Issue with the gearbox was I had a permanent whirring noise, particularly bad above 2000 revs, and increasing difficulty in selecting first or second gear.
My mechanic said it was gearbox bearings, I put it in since it needed a new clutch anyway, had the bearings changed at the same time and since then it's been a beautiful smooth drive and I can hear the engine again. Not the cheapest of jobs mind. Does that sound like what's up with yours?