I knew the reverse light switch had failed as the bulbs still worked in other fittings.
The local Vauxhall dealer wanted £38.10for a new one and fortunately didn't have one in stock....
This one was over £30 cheaper, arrived when the sender anticipated it would.
The switch was fitted in minutes and I now have two nice white reversing lights and don't have to keep using my left indicator to show a little light when reversing in the dark.
The part was easy to fit and works perfectly.