I'd like a box on wheels, for storing spare towels etc.

[minkah]

Has anyone seen or got a good one? I'm happy to paint it/ decorate it, just want something mobile, light, capacious.

Yes - slides easily, v light, lids work well at protecting contents from dust & lids open at both ends of the box. Try www.argos.co.uk/m/static/Product/partNumber/9051036/searchTerm/Underbed.htm or you can get a pair of them www.argos.co.uk/m/static/Product/partNumber/8754884/searchTerm/Underbed.htm which works out cheaper per box. Not sure though how big you want them but I can fit in a fair bit.