2. how do I level it/tamp it - I was thinking of nailing/screwing boards
> where the skirting used to be and using these to get the level correct,
> and using these to rest a board on (with cut-outs on each end) for tamping
> down. Any other suggestions?
You might have problems tamping like this because you won't be able to slide the tamping board sideways to pare off the top of the concrete, and where will you stand? I'd put up some shuttering about 18" from each side, concrete inside this, then remove shuttering and fill in the outside later.
Rob Graham