bof wrote:
If the wash basin wrench is gripping the nut OK try locking a pair of
mole grips onto the shaft/tommy bar to give a bit more levereage. If
that's doesn't shift it, use a stilson wrench to turn the tap itself[1]
using the basin spanner and mole wrench to stop the coupling nut
turning, you can often get the mole wrench to press up against the wall
to stop it turning.

[1] assuming you don't want to reuse it

No, I'm not aiming to reuse it. However this does assume that I can
turn the tap, there is a separate nut holding the tap onto the bath,

IME they turn, unless it's the old type of bath with a square hole and
the tap also has the matching square body.

I can actually get an ordinary spanner or mole wrench or similar onto
the nut it's just that there's not space to turn it. Thus I don't need
to use the basin spanner at all if I just hold the nuts and try to
turn the tap.

I'm pretty sure it's round and not in a square hole as it's a mixer
tap - aaargh, and there's the problem, one can't rotate the tap! :-(

--
Chris Green