Im biased but if you aint into the generic running/cycling scene you could do worse than sign up to a local martial arts dojo / MMA gym and take up some classes as you'll quickly start to take time out and research/learn a particular martial art and its origins/disciplines and it does somewhat take over a big part of your free time which sometimes can benefit you when you're trying to clear your mind / find a distraction.
In terms of the adrenaline rush you mentioned I've done BJJ on and off for about 12 years and even now the rush you get trying to stop someone from attempting to choke you out even just in a training session is immense - its a very humbling experience and one that puts into perspective how fragile life is when you realise it takes seconds for another person to put you out if they wanted
The Midlands has a solid base for BJJ I've been down Birmingham many occasions for competitions - you'll find a good gym down there.
Wing Chun is another I would personally recommend.