Hi Riveralt
Thanks for such a swift reply.
First and importantly, yes I do have an earth and it's strapped to the 'box'.
The original was wired as follows...
TOP:
'A 2Way' - RED
'A 1Way' - empty
'B comm' - YELLOW
BOTTOM:
'A Comm' - RED and short wire to 'B 1Way'
'B 2Way' -...