What’s the best way to clean a slate kitchen floor that hasn’t received any decent care and attention in a while?

You can get propper cleaners for them, think they’re based on phosphoric acid. We did our when we moved in. Hard work with a scrubbing brush. Then sealed it and it looks a hundred times better and is easier to keep clean.

Cleaning and sealing stuff was about a tenner from b and q.

Liberon do stone / slate cleaners and sealers too, and they work a treat.