The message
from "Mike Lyle" contains these words:

Bob Hobden wrote:
"Sacha" wrote
after "Bob Hobden" replied to her
[...]
Marsh Woundwort (Stachys palustris)

http://www.bioimages.org.uk/HTML/T1509.HTM

Bingo! I'm sure you're right. Do we have to worry about it being
invasive
or anything weird like that? I say 'we' because I've asked for
seeds of it
- I think it's lovely!

It's a native perennial wild flower of unshaded wet ground
(marshes,
pond & stream edges, ditches, etc) and is seen all over the country
in suitable habitat. Probably some local to you up on the moor.
Having never cultivated it I'm unsure of it's suitability for
introduction to the garden scene but it does flower late in the
season.

I've grown it, and found it was very durable, but for me not
invasive. But in my particular location it had a rather freakish spot
where moisture was plentiful a few inches below the surface, but
heavy ground under a foot higher beside it tended to dry out in
summer. (The whole of that part of the plot was artificial.) I found
it absolutely delightful, flowering right through to late autumn, and
wouldn't have been without it; but I suspect it might romp away in
light moist soil with little competition. I'd try it. Purple
loosestrife likes rather similar conditions, and is more vivid and a
bit taller, if that's what you want; but its flowering season is
summer only.

I would endorse this but would be more cautious about where to grow it.

I have it in two places. One is a wild area where it is in competition
with quite vigorous grasses. I love it there and in a few years the
patch has quite slowly expanded. The other is in a flower bed where it
arrived uninvited. It does spread. I pull it up once or twice a year and
it returns from roots which are perhaps slightly like bindweed but not
quite as persistent. I wouldn't introduce it to a flower-bed myself.
However, my garden is in the Fens so I guess it's very much at home
here.

Janet G