There are a number of horse dealers, sales agents and importers whose sole business is the buying and selling of horses.  

An advantage of buying from a horse dealer are that they are acting in the course of their business and so the Sale Of Goods Act 1979 and Trade Descriptions Act 1968 apply thus giving the buyer better protection than buying from a private seller (see legal aspects of buying a horse).  However, there are reputable and less reputable dealers around, so before visiting a dealer it is a good idea to do some research ie check the internet for reviews, ask friends if they are familiar with them, etc to ensure the one you intend to visit has a good reputation.  Another advantage of visiting dealer is that they may have several potentially suitable horses at their premises making it possible to view more than one horse during a single visit, and if you don't find one to suit at the time you can ask that they contact you should they get a horse in later that would suit your needs.

Even though buying from a dealer offers greater protection than buying a horse from a private seller it is still recommended that a written horse purchase agreement is obtained from the dealer and a copy of any advert kept as evidence in the event of any later dispute.