While driving last night a car came up on the centre of the screen with rear positioning light failure, so when I stopped the left side lights were in complete darkness.
But when I restarted they came back on but only for about 10 seconds.

Is this a full new LED light that's required?

 

What make and model car? Check the plug for moisture and corrosion first, and then inspect the health of the bulbs to make sure none look burnt out. With LEDs, polarity matters, so make sure if you take a bulb out, it goes back in the same way.

https://www.swedespeed.com/threads/r...arning.593753/
Thread with a similar issue.