Carrying an unsafe load is already covered in law and you can be prosecuted by the police if they stop you and you have not securely fitted your tank.
Most vans have attachments that you can strap down loads that might move and cause injuries, the haulage industry have been using them for years with no problems, and they can carry more than twice what a wfp cleaners carries.
As for waiting for the hse to bring out new guidelines and start enforcing them, there is no problem for all of us, but my grandson who is to be born in April might need to change over to a system that complies with the law by the time he gets married.