Have a look at British Canoeing website. Lots of info for non members (like me)
Membership there also gets you a license for a bunch of non-tidal waters. If we add a canoe to our toys then a family membership will follow.
As I understand it tidal waters are generally unrestricted (subject to launching fees and harbour orders etc.) But be aware if a relative novice that they can carry significantly higher risks than a puddle/non tidal in many cases.
We’re looking at inflatables at the moment but we have access to an estuary / harbour and I have the benefit of having done paddling on tidal rivers in my youth so aware and have previous experience of the exposure/tide risks. I’m still swinging back and forward on the risks / whether I’d rather have a solid boat.