Mostly the Brits choose not to eat horse flesh but it is not illegal to do so.
I sense another underlying issue in this thread - what is it you want clarifying about the horse scene in Britain? Maybe, just maybe, I can answer.
Typically we Brits are a nation of animal lovers, but there as exceptions. Many retired horses, no longer usable, end their days in pastures eating, in competition with the sheep, the abundant grass which grows almost everywhere in Britain.
There is a very significant horse rescue system operating nationally in the UK, most branches of which are supported by charity. I can pay to 'retire' my horse
to pasture should she become unrideable.
However the final outlet for some unfortunate horses and unwanted wild ponies is at the horse auctions which operate around the country. The horses are sold at minimal prices to the horse meat marketeers who ship them by lorry to the Continent where they are slaughtered for their flesh to feed humans or dogs. The horses are following the same route to market as do the sheep and cattle from off the farm. British lamb and beef are highly prized in Europe, but usually the animals are transported alive across the Channel.
As in many other scenarios, we Brits ease our conscience, in this case about horses, by letting the French do the eating.