Johnny B Good posted
However, why not fit another socket below the worktop fed by a spur
from the socket above? This was basically the solution I used in the
case of the dishwashing machine right next to the kitchen sink unit.

In this case, I only had to consider the aesthetics of the job *above*
the worktop.

Adding a spur is too much work. Especially as the cable would have to be
chased into the wall above the worktop, which is tiled.

The best solution posted here is to make an extension lead going from
the socket through the existing hole in the worktop, to a
(free-floating) outlet under the worktop. I could even have used the
lead from the old washing machine, which was already plugged in!

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Jack