Thank
I will move onto the battery next if this does not work.
Sadly, I cannot replace the brake light bulbs without a lot of trouble and extra expense, as I also have the imfamous seized tail gate issue with the cable having become detached at the attuator. Have been living with this as an inconveniece but it appears that the only way to replace the rear brake lights is to drop the tail gate.
Will let everyone know the final result good or bad as a reference should this occur to others.
Thanks again for your help!