Hi Eve, I encounter horses on my commute regularly (especially in weather like we've been having recently) and I've always had good experiences with them so far.
There was one situation where I wasn't sure what to do. I was on a single track road which was lined with dense vegetation, so there was hardly any room either side of the road to pull over. There was a horse and rider approaching me and so, given the narrowness of the road, I stopped and got off. The horse still got spooked though, and the rider looked like she was struggling to control it. I tried talking to the rider and dropping the bike to make myself look as human as possible to reduce the threat perception to the horse, and the rider did kind of get it under control enough to pass me without incident. The thing is, I was nervous of the prospect that if the horse lost it and went for me I would have nowhere to go. Is there anything else I could have done here to calm the horse?