Mornin' Loz, nice shape to the box, and as the timber was free makes it even better.
A couple of tips, IMO I think you need to spend some more time getting the edges, and corners, nice and crisp. Then take a bit more time with your sanding, sometimes sanding can take as long as turning the item. Good job though.
Now go out and see if you can find some more timber in that big puddle. Hope the water didn't get into your house, looks as if it could be nasty for some.