mike wrote:
Just read in a DIY manual that an outside tap should be installed "at
least 250mm above DPC level".

Why? What would be the dire consequences of installing below DPC...
apart from not getting a bucket under it if the DPC were six inches
above ground level?

On a sloping site with the DPC well above ground level, the tap could
be quite high up the wall if you position above DPC.

OTOH, if you have it below DPC, the inner part is going to be below ground.

Much more sensible to run it through the wall at a normal height, then run a
length of pipe down the wall and have the tap at any height you like.

Cue the 'frozen pipe' brigade...