For some reason the content of my left sidebar is being added below the content of the page and I can't work out why. Have a look here
http://floorimprov.thefloorproductio...prov-night-52/

Any thoughts on how to stop it?

Looks ok to me, did you change something?

No, here's a screen shot of what I'm getting

Try disabling all your plugins and see if that fixes it. If it does turn them on one at a time till you find the culprit.