One of these characters is an Irish soldier in the British army. Would a beard be tolerated?
Generally, no. British grooming standards were more severe than most other nations of the time period, requiring soldiers and officers to be clean shaven over Continental armies which were more lax. The only major exception is in British Hussar regiments which allowed men to have mustaches to add a "foreign flair" to their regiment since a Hussar was a Hungarian type of unit that was imported all across Europe after the War of the Austrian Succession.