Regulation 2.(4) "Nothing in these Regulations shall require any person to remove, replace, alter, disconnect or cease to use any water fitting which was lawfully installed or used, or capable of being used, before 1st July 1999."
Was any work done on the plumbing after July 1999?
There's quite a lot in the Regulations and some of it looks really petty - like telling the water company before you do any plumbing, but the significant bit about fittings is that you need an anti-syphonic double-check valve somewhere in the line before the dip-tanks, and it looks like it's also a requirement to have isolating valves at the dip-tanks too - but like I said, if they were installed before 1999 the Regulations don't apply.