Tim Lamb wrote:

Can you see if the other end of the flooring is tight to the
skirting/wall? It might be easier to adjust there than struggle under the
units.

Thanks for the thought, but unfortunately the other edges are under
skirting. However, with a mirror, a stick and some undignified lying
full-length on the floor, I've been able to establish that there's a good
space on at least one of the kitchen walls. The other is hidden behind
plumbing.