Stained kitchen floor tiles

Scarlet Brumfitt | July 30 2021 | SW16

Kitchen tiles have become stained over the years. I’m not sure what the tile composition is but they are very porous; the original varnish / sealant has come off. I have tried using specialist cleaners sold in tile shops with no luck. I read that hydroxide peroxide might be good. Has anybody tried that - is it a good idea?