Jimk wrote in
o.uk:

The programmer on my heating etc is in an inconvenient location &
I want to move it.

The preferred location would involve an approx 8m cable run. I
have some 5 core 0.75mm2 flex.

Can I just stick it on the end of the 5core flex, i.e. extending
the current wiring?
Any electrical or other gotchas to be wary of?

TIA

Can't you go wireless and be more "future proof"