Hi Mags and welcome to GoY and photo would be useful along with the aspect of the bank.

As MG says, picture, and detail of site would be helpful, but meanwhile - you'll need plants which are tough and will perform on what is probably a well drained site. Geranium, anthemis, leucanthemum, trifolium, most grasses, salvia, coronilla, some of the campanula species- it goes on and on.
Is it sunny, or in the shade from the trees for much of the day?

And don't forget the Alpine Phlox and Helianthemums,if reasonably sunny.

In part it depends what the builders rubble is and how much soil there is on top of it, if grass wont grow I would be surprised if much in the way of plants will either.