Citroen C2 - Stripped Reverse Gear?

[KarlF]

Hi

We've got a 2007 C2 Code (basically a VTR variant) and are having problems with reverse gear not engaging (when we lift the clutch after selecting reverse, there's just a slight grating noise from the gearbox). If we then drive forward a bit and try again it will often engage, but then it jumps out shortly after we start reversing. All forward gears are working fine.

I've checked the gearstick linkages at both ends, and I can see that the selector levers on the gearbox are moving fully into position every time (i.e. they're in the same position when reverse does engage as when it doesn't) so I don't think the linkages are the problem. This makes me suspect a problem inside the gearbox, possibly a couple of teeth stripped from a gear?

We've been quoted £600 for a gearbox rebuild, plus about £320 for removal & refitting, which is a lot to spend on a car this age! Or I could source a used gearbox from a breakers for about £150-175, which still makes the bill almost £500 and means taking a chance on a completely unknown box.

Can anyone give a second opinion on my thinking? It'd be a shame to have to get rid of the car as it's only done about 62k miles and has just been MOT'd!