On the plus side, Muddy, you will have excellent drainage from that clinker. The minus side is that the soil is fairly shallow. To improve the soil and build it up I would advise lots of garden compost or soil improver - could be a bit expensive if you have to buy it in. Maybe raised beds for the veggie area. These could be as deep as you think necessary and filled with good soil.

Raised veggie beds would definitely work if you can raise them another foot above to allow for things like parsnips and potatoes. Talk to your friends and neighbours about any garden waste they may be wanting to get rid of. The quickest but more costly solution, in the short-term, would be a delivery of good quality top soil, which you can mix with any compost you get. Also the bed of river clay will help to keep your moisture content in.

thanks to both for your advice i will have a good think over the winter, at the moment raised beds seem the best way forward. again thanks for the help given