Arthur wrote:
I'm really looking for what is a stand-alone one-hole mixer tap with
matching standard tap.
The holes for the two hole basins will be clearance on 1/2" BSP. which is
like around 23-25mm. You might be able to make the hole bigger with a
diamond drill but you need to make sure there is a large enough flat area
under the basin to connect the monobloc.
thanks for the warning, Ed.

If you're wanting this because you want a separate tap for potable water
at the basin, you might be able to use a thermostatic mixing/blending
valve combining H&C to one single tap for warm water at a preset
temperature for washing purposes, and the other single tap for potable
water.

If you have another application in mind other suggestions may be
forthcoming if you can say why you want to do this.

Owain