Rear saloon high-level brake lights

[SG77]

Hi, could anyone please advise the steps to check and repair the high-level brake lights on my b6 saloon.

Is there a specific fuse for this or is it the same fuse as the ordinary brakes?
There is a panel across the roof at the back covering the lights, is there a way to take this off and once off is it a total light unit replacement or can you replace individual bulbs or somewhere in between?

Many thanks

Spencer