Thanks fitzer, bhg.
As I linked in the other thread, what I'm doing is this:
https://www.skylineclotheslines.com/product/pulley-clothesline-kit-8-inch/
which would mean that Mrs A would walk out onto our decking (no steps involved), peg the washing to the line, and feed the line away from her (or pull it in to bring it back).
Linepost.co doesn't seem to do those (in fact only Americans seem to use the system - Mrs A says Brits only use tumble dryers these days).
But kicking it around with our friendly (inventive) builder, I think we've cracked it, one way and another.
I'll post pics of the finished article in a week or two!
A