I have just finished Pony from Fire, still not worked out the strange title though, and took a while as I kept putting it off!!! Not exactly as I had predicted but I was pretty close. Firecat arrived a wild and dangerous pony who had killed a man. Yoland, still very nervous, ends up saving him from a fire - Is this why it is titled Pony from Fire? - and of course from that moment on she and she alone can manage the beastie! Her, quite frankly, awful dealer of a father keeps blackmailing her (as if the poor girl hasn't been through enough all ready) and at first it's if she doesn't ride Firecat he will be destroyed then because she won't compete him he is sold........along the way just like Carmen she has to make a desperate ride to fetch a vet, during which she falls, bangs her head, voila - memory begins to return. As can only happen in a pony book the pony no one but her can handle turns up a show and she is asked to ride him (who was originally riding him is anyones guess as when her brother tried him he went 'loopy'). But anyhow she does because she thinks it will stop him being destroyed, but is it too late? (Thankfully) she didn't win the class but did enough so as on her return home she finds Firecat is grazing in their field. Cue happy ending.
Better than I thought it was going to be and a definite improvement on The Mystery Pony but did leave me a little disappointed as these titles are so hyped up.
I still cannot find an author who is a patch on Josephine Pullein Thompson and Caroline Akrill but the search will continue. ( NB I have not included Elyne Mitchell in this as her books are so different from the average pony story.)