It would be helpful if you could tell us what you intend to grow in the bed.

Veg

You will still need adequate drainage, Nick. Depending on what the pond is made from you need to break up the base to allow water to drain out, otherwise your soil will become waterlogged and stale. You can then fill it with whatever suitable soil/compost you think fit.

That's what I thought you were going to say... Back on the shovel it is then :)

Good way to use stones that get stuck in the fork.
Collect up in a bucket and drop in the bottom of the hole.

Definitely a good way to get rid of 'hard' rubbish Diane. But make sure that the stones have some soil mixed in with them so you do don't get voides. Soil from above eventualy filters down into the voides and the surface of the raised bed will slump.