Alsohuman the first sentence of my post is below - it says reactive quite clearly. Hence my response.
Just returned from a dog walk. Huge (huge!) empty field, reactive Ddog playing happily off lead with her toy as no other dogs around
finneganswhiskers we don't go to busy places or at busy times. this is an absolutely massive field that usually has about 3 other people/dogs in it max (it was 6am this morning and until pest dog turned up there was no-one else there at all), there is plenty of space for everyone to keep away from each other, and everyone usually does, been going there for 3 years with no problems until today!
There are many popular, prettier, busier, nice dog walking parks / open spaces nearby, this is not one of them! We drive past all of them to go here for precisely the reasons you say.
Ddog is even more reactive walking on lead in proximity to other dogs, so other than keeping her in completely, or hiring a private field (which we do, but the nearest one is 20 miles away so not a daily possibility) this is the best option locally.
Re other dogs, she will allow a bit of a bum sniff and a hello, but her body language is very tense, and she clearly doesn't want to play, and will snap if the other dog won't leave her alone. Usually the other dog reads this and wanders off, or the owner calls it away, no problem. We take her to classes where she is learning to socialise, and it's good for her to see other dogs at a distance for positive reinforcement.
My post this morning wasn't really about my dog as such, it was more about the owner's attitude, and in response to the OP - it kind of doesn't matter that it was my dog it ran up to out of the blue, it could have been a small child who is scared of dogs, or someone with an allergy, or someone on crutches. It was the owner's surprise / indignance that I expected him to have some sort of control over his dog, or just pop it on a lead for 2 minutes, regardless of my reason for asking. Most people understand, even if they don't like it.