There is a new British Standard for the installation and commissioning of Rainwater recycling systems. This is a useful document and gives plenty of common sense information. Unfortunately, you have to pay for the standard.
There are many companies out there that can do a competent installation, in fact, you could do one yourself. Applying the basic building and plumbing rules to such an installation will get the job done.
Currently there is no legal requirement to use this standard in your building project.
Do pay attention to detail when planning a recycling system and think through the requirements that you have. Also you will most likely find it easier to do the installation of the tank early on, so always lay out a full sized DN100 pipe for the cables and water pipe. You may put these cables in at this time and simply wrap the ends up in a box or bag.
It is very easy to loose the extra units, so be sure to put them in a safe place !
