24 volt battery charger

Yes that is correct.

It is absolutely imperative that none of the standards, code of practice (not to mention legal requirements) appertaining to emergency lighting are referred to when designing such equipment

It is, for example, far better to have a mickey mouse low battery drop out circuit operating at a level determined by the local hippie community rather than that given in the standard for the construction of emergency lighting.

Sod the necessary slog of competent design - just get a good lawyer

Exactly - for similar reasons one usually does *not* do any patent/IPR searches as part of a design because it is cheaper if we accidentially step over some toes than delaying product. That's the legal deparments advice anyway - they all drive nice cars, probably ;-)