I've found it.

The ill remembered Latin was actually Parvus Numero, Magnus Merito.

The crest, with an RAF-like eagle facing the other way, is surmounted by an arched crown with five visible supports, unlike the three of the RAF.

I read the Germanic scroll as Koninkluke Luchtmacht, but it was actually Koninklijke, which is a giveaway, or would be if I had worked it out before googling the rest.

It's the Royal Netherlands Air Force, small in number but great in merit.

They have an eight pointed cross beneath another crown as a medal hanging from the crest by a ribbon and bar.

Pity I didn't write the thing down accurately at first.

I did not buy the house from anyone from the Netherlands, so its history is a mystery.

And it will come off with a razorblade.

Thanks for the interesting discussion.

Penny