I know that there are regs regarding power sockets in bathrooms etc. but
are
there any guidelines about the proximity of power sockets near a sink.

There was no standard distance last time I looked (I don't have the absolute
latest regs). However, there is a general rule that sockets must be suitable
for the location in which they are installed. This is usually taken to mean
30cm from a sink. Personally, I wouldn't be too concerned with distance from
a draining board, provided it is a reasonable height above the surface.
OTOH, they aren't particularly useful there as the leads trail on the
draining board, so an additional socket in a more convenient location would
be better.

Christian.