We do not maintain a database of all polo clubs on the website but Swim England, water polo’s governing body in England, can provide you with the info you need. We recommend you try this link > https://www.swimming.org/waterpolo/finding-english-water-polo-clubs/
University water polo competitions in the UK are provided by 2 organisations...

Great Britain finished 9th at the European Championships after winning a fierce battle with Serbia 10-9 (1-1, 3-3, 3-2, 3-3) in their final game. Winning 4 games on the bounce, the Great Britain showed great resilience after 2 tough opening matches.
Theo Nousios’ side had to dig deep in their final game– and survive a four-minute exclusion – to earn the narrow victory and end their campaign on a high,