By far the best thing you can do is to join a local club
, try out a variety of kayaks, use their equipment, but most importantly, get some coaching which will improve your paddling and safety skills. You'll also make some kayaking friends to go paddling with, at least until your skills are up to being safe paddling alone. You'll also need to set aside money for PFDs and suitable clothing.
Don't spend money on a kayak yet. Invariably, it will be the wrong one if you go into this blind without trying a variety of boats. Local club to you is probably Fife Canoeing Activities Group http://www.fcag.co.uk/index2.php