Thanks Jason. That works. What exactly does it do?
The only problem with it is that now when I try to re-edit the form I cannot do it unless I go to Code View. If I take out the overflow: hidden; code I can re-edit the form using Form Builder. Strange. Ok, so I can comment it out but and un-comment it when finished but it's a bit of a pain. Actually, it affects all the code on the page (see attached screenshot).