Best thing to do is to look up dog show central. This site tells you when and where the next shows will be held.
To get into showing you need first of all a dog that has potential to win (otherwise it wouldn't make sense to enter the show ring). A good pedigree to start with may be helpful although it is not a guarantee as you don't know if the pup is going to turn out good enough to do well in shows.
Second thing that you need to know is that many breeders show their dogs which means that they bring the best of the best in the show which makes the show environment very competitive.
Third thing that you need to be aware of is that usually breeders keep dogs with show potential and sell the rest as pets. They need to do that to continue to win and improve the reputation of their kennel. Rarely they let go very good pups.
What you could do is go to shows and see what the environment is like and take it from there. I live in the UK as well and competing in shows at top levels it's hard as the environment is very competitive.
Google ring craft training in East Sussex.
Turn up and it's as easy as that. Let us know how you get on. If you can't find anything I ll have a look for you
Find ringcraft classes in your area first, this will teach you how to train your dog ready for shows, also I have a list of shows in the UK on my calendar I can give to you if interested, going to shows to watch is a good idea so you can look at the standard and what it is all about first