I don't recall, either, and even Wikipedia doesn't have much, but apparently, there was http://en.m.wikipedia.org/wiki/British_Military_Mission_to_P.... There also is operation Freston, an SOE operation into Poland in 1944. In neither case, I don't think the Brits fought against Poles, but certainly in the second case (at least, that's what the many links with limited information point at), they invaded Poland. Operation Freston even has a book: http://www.amazon.co.uk/Operation-Freston-British-Military-M...

(Given the scarce information, this could still be a hoax, but if so, I fell for it)

I haven't read the book, but I can only imagine that a lot of creative liberties would need to have been taken - otherwise a surprising number of these countries wouldn't have existed at the relevant point in history.

eg, Poland was part of Russia during the 1850s Crimean War, and a little poetic license could stretch that a long way.

Having found further references, it seems most the book's claims for Poland hinge on actions in & around Danzig while it was part of Prussia - now being Gdansk, part of Poland.