Since the usual source of information doesn't seem to help I thought I'd try here. Need to replace the tap in the kitchen sink, but the existing pipes are solder jointed, so I need to cut them to install the new tap (really don't fancy messing around with a blowtorch under there with all the plastic waste pipes). However the existing pipes are also painted – can I use compression fittings straight on painted pipes or do I need to remove the paint first? If I need to remove paint, what's the best method to leave a good surface for jointing?

remove the paint with sandpaper is what I do. Nothing too course

I'd finish off with wire wool run radially.

Give it a scrape with the edge of a chisel & most of it will flake off, before using the sandpaper.

Yup, you'll need to remove it first or it will leak past the olive.
Scrape the majority off with a stanley blade, then go at it with steel wool. I usually burn it off with the torch though then buff up with steel wool

I usually burn it off with the torch though then buff up with steel wool

Yeah, that seemed like the obvious way, hence why I mentioned I wasn't keen on the idea in that location!

scrape the paint way with a craft knife
Then burn and clean the pipes