Thanks, BigCat

Yes I want to be regs compliant and will look at running a return 2.5 for
the socket circuit.
I have found one or two nasties, mainly associated with extensions, the
original wiring seems sound.
Although the original 70s wiring can take some sorting on occasions, with
lives looped around switches and neutrals around ceiling roses - very
strange, but standard for the area and era apparently!

Currently the 2.5 is clipped along the inside wall of garage, through the
end wall between ceiling of extension and upper floor then down "top hat"
type conduit behind plaster to sockets.

What would you recommend to protect the 2.5 in the garage?
I am considering running the feed, return and lighting cable in some kind of
trunking.

TIA

Phil