Southend-by-sea BSAC 22
Driving 90 minutes to go diving would be considered reasonable by most divers I know. I found this by using google maps and google within 3 minutes. I have never been diving in the UK.
However, we have similar diving conditions in Norway, and I absolutely recommend diving locally. To really get in enough dives to become proficient and enjoy being underwater, you need to dive wherever you are (or be a millionaire and travel every weekend).
Yes, buying equipment and a drysuit is an expensive investment, but you get so much in return, and when you have the gear diving locally is not that expensive. Diving wrecks in black, murky water is very exciting, and once you focus on the art of diving it's not just about your environment, but also about honing skills or just being present. It also makes dive trips more exciting as you can fully enjoy a change in scenery while the technical aspects of the diving is second nature.
Contact a local club and see if you can rent a drysuit and get a drysuit class or something. Just do it!