Probably best easiest to run a new wire across

Use a piggy back fuse

as an auto electrician with 40 years experience the rule with multiple faults is to pick on one (easy one) and put that right ...that usually sorts the others Always listen to old people or when they die you will live on in ignorance.
The avatar is a picture of the man with a big cock.
Learned to 4x4 on 100 mile beach and Frazer Island QLD
Dont spend money on old cars you will never get it back

Sorry for slow updates.

Ok, following Andy K advice I ran a new wire from the original fuse in the cjb round to the drivers door pillar and made a connection there. Hay presto, door switches now all work as does the central locking for some reason.
Now need to sort out why the head unit is blank and have an error code about lost communication with audio unit u0184.

..............as does the central locking for some reason...........

Read my post above again and you will understand Always listen to old people or when they die you will live on in ignorance.
The avatar is a picture of the man with a big cock.
Learned to 4x4 on 100 mile beach and Frazer Island QLD
Dont spend money on old cars you will never get it back

Cheers
Col

Thanks Col