Landowner is absolutely right, iv carried out both his suggestions and it works.
I removed all my indicator, side and brake light lenses as they looked twenty years old, popped them in the dishwasher (while wife was out) and they look like new. Refitted them with a good lube of silicon grease, keeps everything out.
Iv changed my brake lights and side lights for LEDs and they both look good and have lasted ages. I'd like to change the indicators to LEDs too but iv heard that it's expensive as you need loads of extras to be added, something about how they flash.
If I find a set of LEDs that work and last in the dials I'd let you all know.