12 miles in a WW boat would be a challenge.. A touring boat will
typically be 16 - 18 feet long.
You will get all kinds of opinions about beam, rudders, seats,
material, paddles etc. Most of it comes down to personal prefference: A
WW boat used for touring is something most paddlers will agree is a
mistake.
I play in WW as well as the big bad ocean; different boats and
different purposes.
I would recommend you hook up with a touring or sea kayak but before
you do membership in a club may be a fine investment. Clubs often rent
or loan boats, have acces to information and the odd time special
pricing on stuff.

Good luck with it all , you have some of the worlds best paddlers to
play with in the UK.
Oh; Justine Curgenven has a video out ( This Is The Sea) that is a nice
flick if you can rent borrow or even buy it.
You are entering perhaps the greatest sport in the world that will last
a life time.
Alex