In reply to climbingpixie:
I had something similar on the moor above Wharncliffe recently, a couple teenagers had started a small campfire. Tried to talk to them with no success, so tried to call a ranger for the forest, but none available and they advised to call 999. I was initially hesitant like yourselves as it seemed a bit overkill, but they were excellent and sent a small team with beaters and buckets proportionate to the response needed.
So essentially I'd really encourage anyone to call 999 about a fire they are at all concerned about, you aren't going to get the fire bridge blazing down on your in a big red truck necessarily!