a few questions:

whereabouts in the UK are you?

have you considered joining a camera club?

Which sport(s) are you going to cover? To be a good sports photographer, you really have to know your sport(s)

I wish you well in your desire to become a pro sports photograher, but I fear it's a big challenge. It's a very compettive field and can be very time consuming. Takng the pictures is only part of the job. Processing, editing and getting them to potential clients is going to be a very hard part. Being a skilled photographer is only part of the role, being an entrepeneur is an equally important part.

In terms of equipment, Canon, Nikon and Sony all make equally good cameras and lenses. You need to handle all of them to find the one that feels best for you.