Living in such a damp and mild climate like Ireland is. Raised beds are definitely the way to go to improve drainage. Years ago when I lived in Blighty I would dig over my allotment and allow the big clods of earth to be broke down by the frost and rain.
I decided to make a raised bed yesterday from old pieces of wood I had left over like some old cracked scaffolding planks, some posts, my stash of cardboard boxes and my homemade compost.
I didn't even use any screws or nails. My tools were my trusty bow saw and my timber axe that I used to knock the posts in to support the planks: