Once upon a time, I worked in Health and Safety, and spent a lot of time learning my way around the various UK legislation.
No surprise - factories were the greatest generator of H&S rules, but fairgrounds were in second place behind them (third, slightly surreally, was herring processing).
The understanding that fairground rides of any sort can be very dangerous has been with us for over a century.
Rospa have a whole page on bouncy castle safety
here, which links various other documents.
Okay, with an aeronautical engineering degree, I could work out the loads on a castle and safe values on anchor points fairly accurately in half an hour. I wouldn't expect a fairground type operator to have my level of knowledge - but I would certainly expect them to understand RoSPA and related rules and guidance, and have access to rules of thumb on when things get dangerous. If there's evidence they didn't, there's no excuse.
At Shoreham, yes, perhaps some double standards - but the most recent AAIB report does certainly show where some serious questions might be asked of the FDD. On the other hand, maybe they have, and we just don't know about it.
G