Reverse Light Switch

Hi All,
I'm finally getting around to fixing my lack of reverse lights, so I need some advice on the problem.
The reverse switch that is in the gearbox only goes to ground when you hold the stick over to the passenger side of the car (when reverse is selected) - if you move it over to the right it breaks the contact.  I know the switch can be screwed in and out of the gearbox to adjust the switch, but it appears to be screwed all the way in.
Is there somewhere else an adjustment can be made that I'm missing?  Could the switch be broken/worn down?  How do you adjust it properly?
All answers gratefully appreciated!

Thanks for that mk1escort2build - I tested the switch using the continuity function on my multimeter (continuity to ground), and I found out that holding the gear lever over to the passenger side makes the circuit, and leaving it alone or pushing it to the driver's side broke the circuit.  I'm thinking of just picking up another switch and swapping it over and seeing if that works.
The only other thing I thought could be wrong is that the gear lever is quite 'sloppy' - there's a reasonable bit of play once a gear is selected.  Does anyone know if maybe the selectors need adjusting?  I thought that if they do it could be exacerbating the problem with the switch.
Forgive me if this is an obvious thing to do, I haven't had a lot to do with gearbox work!!

Cheers for that David W - I have to take it out to check which switch it is anyway, so I'll try the soaking in petrol trick.  I thought that it might be adjusted incorrectly because it seems to have a locking nut on it - but that could be the problem too I suppose!