I didn't think this would be necessary but, as I didn't really know what a safety data sheet was, I investigated further and rang the Health & Safety Executive.
The man there said he couldn't speak for stores - I would need to speak to Trading Standards - but he did know about safety data sheets. These are issued by manufacturers and suppliers who share an obligation to ensure that certain products are used safely. But, if the product is for resale, then the guidelines will all be on the bottle so there would be no point in putting a safety data sheet up.
Bleach for resale, he concluded, would come under DTI legislation for consumer protection and would be presided over by Trading Standards. I rang the Trading Standards Institute, which suggested that Health & Safety was the place to go for info, so I think we can safely say that shops do not come into it.