Just an update in case anyone else needs some of this cable,
I got some 11 core + earth cable from my local electrical supply mob. (Middys) Thanks Mick!
They had to order it in, and they list it as 'Cable rubber flex 1.5mm 11 core + earth submersible'.
It has an Ozoflex mark on the outside.
I didn't really need the 12 cores, but this cable is the right diameter to fit the NATO plug for a tight seal, and looks original.
The best bit is, all of my lights now work, including the blackouts, and there are even some spare cores!
Thanks for the leads Mick and Muddy, much appreciated.
Cheers,
Mike.