what you are looking for is a sit on top kayak! angler versions hold there money well! but you can easily kit out a non angler one. not sure about second hand but you can expect to pay from 500 to 800 for the yak itself or even more if you want a top end one! then maybe same again for your kit! i paddle a prowler 13 angler which i find a fantastic yak nice and fast and stable with lots of storage. but have to say a fantastic way to fish even when your not catching :laugh: not often you find someone else fishing your mark! unk:
Have a look in the "for sale" section on the anglersafloat website. this will give u a good idea on what u should expect to pay. One advantage of buying a second hand fishing yak is that it will probably come fully rigged with a few extras thrown in.
There's a fantastic kayak for sale in the classifieds here... Tarpon 14. You shouldn't spend more than £600 for a used kayak with all the accessories (paddle, anchor, Fish Finder, removeable seat.
Go to planetseafishing.com and speak to Neil... he may be able to point you to some local kayakers. I met a chap down at Drummore from your neck of the woods but didn't get any contact details for him.