Thanks for the replies.

The car was in and out of the garage after a few hours yesterday morning with a bill of £38 with a future bill of about £50.

It turns out that the cogs for Reverse, 1st, 3rd and 5th weren't fully selecting properly, so they adjusted the cables and adjusted a few other things (none of which I'll prob understand) and now everything is selecting fine.

They've recommended I have the gearbox serviced and the oil in it changed as the gears not selecting fully may've ground down some of the cogs and left small deposits of metal in there, so aside from this everything appears to be fine