Hello, I hope I can be of assistance.
Is it both sides that are coming on then fading or just one side? Do the stop lamps and other lamps all work OK?
Let me know and I'll reply as soon as I'm able to.
Stops and indicators still work, have lost both tails and number plate
Hello again, I hope the following helps.
Start with checking the bulbs and wiring to the number plate lamps, as far as I'm aware if there is a concern with the number plate lamps this affects the LEDs in the tail lamps, the LEDs flash on but then due to the number plate lamp fault too much power is going through them and could damage them, this is why they go off again.
Make sure the wiring to the number plate lamps hasn't rubbed through. If you can't find any wiring damage then you need to check for 12 volts at a number plate lamp connector, of there isn't 12 volts then check the fuse and if this is OK you need to trace the wiring back from the lamp checking at intervals for 12 volts. If there is 12 volts at the lamp connector make sure the earth is OK.
Let me know if I can assist further and I'll reply as soon as I can.