As Pete999 said, give them info to read (or links to it). Some useful resources are:
www.beama.org.uk
www.beama.org.uk
www.beama.org.uk
They may not be the best guides, but they are sort-of independent of any one manufacturer, and more importantly they are not "you" pushing for a sale. However, hardly anyone will read them,
or understand them, so sometimes you need to provide a short recommendation of what you think is best (obviously that is real in light of available guidance).
For example, if I were writing to myself on my own CU it would be something like:
- I recommend the fitting of a Surge Protection Device (SPD) as the 18th edition of the wiring regulations recommends this for most cases, except when a risk assessment suggests the cost of the SPD outweighs the probable cost of damage. Most households have a lot of electronic equipment and so the modest cost of the proposed 'Type 2' SPD is less than the effort of properly assessing the risk.
- I would recommend the use of an all-RCBO board over a dual RCD board as there is a small total number of circuits so the slightly higher cost is outweighed by the reduced the impact of any nuisance trips or futures fault (as well as reducing the cost and time to locate any that do arise).
- I would not recommend AFDD in this case as the property is not in the high-risk category and the high cost of AFDD at this time is difficult to justify. Other steps to reduce the risk or impact of fire, such as a full linked fire alarm and/or some extinguishers would bring greater benefit.
Of course, that would vary depending on what you are looking at doing!