I would lay out over a foot deep of rotten/spoilt hay and then, once it flattened down I would lay a row of compost OVER the hay to plant into.
The plants roots went right through the hay under the compost and it all grew veg super.
That was in Florida when I was growing into pure sand and was the only way I could get anything good out of the garden.
No reason to think it wouldn't work in the UK so give it a go.