The boards were originally covered in peeling stained cork tiles, stripping these off left a layer of old glue and bits of tile on top of a layer of Ronseal’s best varnish.
However a quick run over with the belt sander left a clean surface. I used 40 grit so the surface is not too smooth, then I hope a layer of clear matt varnish will seal the surface without making it slippery. Next year we can paint the floor or put a complete new floor down.