It doesn't sound a friendly place for plants if you can only go down 8 inches where would the roots go? have you thought about a feature eg large pot or statue or whatever suits your garden,or even a shady arbour which will catch the evening sky, have a look through photo's here for some interesting ideas

pick a scented Viburnum, or maybe choose a hebe you like? I'm not sure it's quite time to plant yet, I think I'd wait till Spring, but once established they are both as tough as old boots in our garden, and I think their roots would do some creative searching for more goodness among the rubble etc! They are not fussy plants, at least the kind we have aren't. If you are interested I'll try and find out the name of the Viburnum we have?