Unstable pages

I am hoping to create several product pages like this

http://furnituretoyourdoor.co.uk/?page_id=224

Although they publish ok at first if I add more text I seem to be loosing my Checkout button, or if I move the layout around I loose the Checkout button. I've tried putting it in its own cell but this did not work, anyone managed better than me with this? The problems seems to be adding images to pages, is it that I am obscuring part of the page?

Thanks