On Wednesday, 20 March 2019 15:09:22 UTC, wrote:
As part of re-wiring the workshop I want to be able to pull down a
socket (on a flex) from the ceiling when required and then to have it
retract when not needed. The action would be something like a roller
blind: pull and let go to latch down, pull again to unlatch and retract.
The roller blind mechanisms are quite long and fit in a tube whereas I
need something that winds a string.
What do I need?

I have never seen anything like that.
You could have a non-retracting one using a socket from an extension lead and a flex outlet plate