I have this cover through the RAC and its supposed to be second to none! Good value at £45 for the year and loads cheaper than breaking down on a motorway and having to pay an awful lot more if you were unfortunate enough. Not had to use it thankfully. The RAC value their customers, especially with horses, I know this too well as my OH is an RAC Patrol!!
Hi I currently work for a horsebox hire and sales company and have heard some nightmare rescue stories, one involving a company that came and rescued the trailer and car but refused to take a live animal so they had to get a transporter in to load the horse on the motorway to bring it home another was rescued to the nearest services and left there. I would recommend the equine rescue service. It starts from about £48 pounds and they will rescue both you and your horse or if to far your horse will be brought to a local reputable livery yard for the night and then returned home.
I broke down on the M25 I got my referral for this company through the AA they are based just of the M4 nr hungerford but brilliant recovered me and my pregnant mare without any undue stress. Top company if you interested I will look them up have not used them in a while as have been to busy to compete.