Oh, how plans change! I was up there on Saturday lifting the flags up (photo's on site, link in sig) and there was nothing but a load of hardcore and sand under the flags. But, as you can see from the photo's I now have four perfectly defined beds measuring 12ft by 4ft with a nice solid path between each.
I'd be on forever digging all the hardcore out so my plans for this now, are to obtain wood (from dismantled lofts) and build raised beds and fill with top soil.