Welcome to the forum.
You mention something that can be stowed away easily? If you're looking for something to launch and retrieve that can be dismantled and stored, then you're probably looking at a SIB (soft-inflatable boat). If you have space for storage all year round, then a RIB (rigid inflatable boat) would be the way to go. As with anything, budget plays a major factor.
If you're fishing, then your 1/4 mile limit will undoubtedly change as your confidence increases and weather conditions allow, resulting in you venturing further offshore. These boats are perfectly safe the further out you go, but that's dependant on your experience and knowledge, reliability of the engine, back-up auxiliary engine, means of communication (VHF), safety kit, etc.
There's a few guys on RIBnet that use Zodiac Futuras. These are great inflatable boats and very capable. They have (speed tubes) that run under both inflatable sponsons which aids plaining. In addition it has an inflatable keel, and they come with the option of a solid sectional aluminium floor, which helps the rigidity of the boat and is perfect for lashing down fishing gear, fuel tank, and general gear.
Engine wise (bearing in mind you're a big lad
) then 25hp is probably about the most I'd be prepared to manhandle in and out of an estate car, ideally with help. Better with a box trailer if you had space to store. The boat itself comes in 2 bags. With experience - you can arrive, build and launch in around an hour.
I'd suggest something like a MkIIC. More details here: Zodiac Marine - Boats - Futura Mark II C Alu
Engine wise, then a 2-stroke would be best. It doesn't mind being stored on it's side (4-strokes are heavier and must be stored upright). They also use a short-shaft. Something like this Mariner 25hp would be ideal: John Bridger Marine