I dunno how rare the PAL version is, but word is, it's pretty scarce. As for it's worth? Probably a good $15-$20 at least, based purely on its scarcity and gameworth (i.e. it's a pretty dang good game).

You can read my thoughts on the JP version here: THE FIREMEN

I read about it in EGM in 1994 and have been curious ever since. 12 years later I finally got to play it. Solid solid game. As for the difficulty, it's really easy once you play it 4-5 times. True, it's a pity the game is so short. An option for random generation of fire location wouldn't be shabby either.