None of this needs to be bought at once. Building a complete kit over time, prioritising the areas most exposed in a typical fall, is a realistic way to get there.
Any impact, including a helmet dropped from a moderate height, can compress the inner liner in ways that are not visible from outside. A helmet is designed to absorb one significant impact by sacrificing that inner material, so a helmet involved in a crash should always be replaced, not inspected and reused.
Daily wear also plays a part. Sweat, sunscreen and regular use all shorten a helmet's working life, so riders who use a helmet every day should expect to replace it sooner than someone who rides occasionally.
The trade off is scale. A workshop like this will never produce helmets as fast as a large factory, and that is treated as acceptable, since the aim is a considered, well finished helmet rather than the fastest one to market.
From there, the build follows the same certified construction as the standard range. Made to order does not mean a shortcut around testing, it means the standard process is carried out around one person's measurements and Hedon London preferences instead of a general size run.
A clean visor is a safety item as much as a comfort one, since scratches and haze scatter light and make it harder to judge distance in low sun or at night. Clean a visor with lukewarm water and a soft cloth, and avoid dry wiping, which is what causes most fine scratches in the first place.