Thanks for the suggestions. The mirror screws would work, but may stick out too much aesthetically - the basin is really small, screwfix code 93495.
The two-part plasic screw covers would again stick out a bit. The slimmer single-part screw covers wouls be OK. I've got a few in the cupboard...
I've bought a small cloakroom basin with two tap holes, slotted overflow and a chain stay hole. This was the only configuration in which a basin was available to fit our very small downstairs loo.
Due to the small size of basin, we'd like to use a rotary plug/waste, i.e. the type where the...