TM, if you are still using the Lucas
SPB401 3/8 unf threaded switch then even by making it accessible the switch still fails as it is unreliable but it is easier to change.
Luckily it's also unreliable in Morgans and the owners club has found a more reliable alternative.The Brake Light Switch on traditional Morgans seems to be a component that 'regularly' fails.https://sites.google.com/site/morganatica/06-electrics/switches-and-relays/brake-light-switch
The Intermotor 51610 (Lucas
SPB401) with 3/8" UNF thread fitting Morgan 4/4 and Plus 8 1975->
So do both fixes, better location and the better quality Intermotor 51610.