Photography is unfortunatly one of those businesses where there are loads
of mediocre/ok photographers and very few GREAT photographers! Work can often be hard to come by because you're relying on people liking what you do to get paid. And again, unless you're very good - you're not going to get as big a client base.
You can go to uni to study photography, however you'll find that the majority of professional photographers (possibly with the exception of proper, country/world level sports photographers) won't have a degree, just a passion and love for what they do. I'd suggest try and get a job as a photographers assistant, you'll probably find yourself running around a show ground carrying a monopod and two heavy DSLRs that are worth £1000 each in the rain but it'll be good experience, if you want to go into sports/horse show photography.
is a good forum to look at, yes it's a Canon biased forum but you have a wide range of people on there from hobbyists to people who regularly sell their photos to Nat. Geographic
Most people on there would support the view that you have to be very good to get anywhere fast and you have to be *incredibly* dedicated.
It also takes quite a lot to set up to a professional level, £400 could get you a nice used Canon 450D with kit lens, if you can get another couple of hundred you could get a new one (not sure what the current model is, sorry) or a used one and some nice lenses. Unfortunatly the lenses that you'll find most of the professionals using are £1000 pieces of glass... sat on a £1000 body