Rooster writes
Have been trying to identify a trailing plant with white flowers just less
than 1 inch across which are seen probably for 6 weeks or so from March
onwards in the UK. Can anyone tell me what they are? My neighbours have them
but of course they don't know either. Hopefully an easy one for somebody to
answer.

A white flowered Vinca? Try a Google images search. Or do you mean
something which trails down walls as opposed to trailing across the
ground? In which case something like aubretis, only that's usually
mauve.
--
Kay