Don't want to burn bridges though so was still going to have a DSL socket upstairs. Plus, as I have some wired-only devices, I need wired ethermet from the cupboard back to the lounge. I think three connections should suffice.
I just want to make sure I'm on the right track here: what I'm expecting to end up with is a faceplate in the lounge with four ethernet/RJ45 sockets, one is DSL in (and marked as such) and the other three terminate in the below-stairs cupboard. And a similar faceplate in the cupboard - one DSL in and three other sockets. In the cupboard I just connect the ethernet outs from the router to the faceplate sockets, then upstairs I connect my wired devices to the sockets there.
Is this an unusual kind of arrangement? Any problems with having two DSL sockets (obviously only one will be in regular use).