IIRC all three phases are wired to UK homes, but only one is used.
Installing a three phase meter should be possible, but I am not sure
of the cost.

Some UK homes may have all three phases connected, with only one used,
but this is by no means universal.

I believe that it is common to wire a street of houses up so that a
3-phase cable runs down the street and each house is supplied from one
of the phases by a short spur. I think that they alternate the phases
so, for example, number 1 uses blue, number 3 (next door) yellow,
number 5 red, number 7 blue again.

I have also heard tell that streets with overhead supplies used to
suffer from over-use of the blue phase as it was generally the bottom
wire and so easier to tap (though this may simply be a myth)