On Friday, 9 August 2019 14:12:55 UTC+1, Peter Johnson wrote:
I spent 30 years in fire service communications and would have no
difficulty with that. Inputting locations using grid references was
never considered for the two systems I was involved with and I suspect
that the cost of putting in place a system that could accept them
would have been expensive and rarely used.

When I were a lad there were TV adverts encouraging farmers and other remote dwellers to print their OS grid ref in big letters next to the telephone for use when calling the emergency services, so they must have had some mechanism for using it.

Probably a paper map as I don't think "systems" were in use back then.

Owain