If you want to start learning to swim or if you are wanting to take your swimming to the next level then the best place to head is to your local swimming club. Most swimming clubs will have teams or lessons depending on your ability and what it is you want to achieve.
The first place to go is to your local swimming pool. Most swimming pools have a local club contact or can advise you on who to speak to. If you are from a very quiet or remote location then you may only find basic swimming lessons. If you live within a town or city
you are guaranteed to have a swimming club close by and in your area.
The ASA is the Amateur Swimming Association, a group which coordinate many swimming events and have a heavy club involvement. These would be your next stop as they have their own swim schools directory which is ideal if you are on the search for swimming lessons. There are 1151 swimming clubs within the ASA and this page can take you to find swimming clubs in your region.
Swimclub UK is an online forum for swimmers which is open to all kinds of swim related questions. If you are struggling to find anywhere, why not post a question on the forum and you might get a good response.