Is anybody aware of current recognised guidance or ACoP that specifies the minimum height of a fire exit. Many guides (ADB, BB100, 9999 etc) specify minimum exit widths for said occupancies, however, no mention of minimum exit height. A standard UK door is 1981 mm in height which comes from the old 6ft 6in imperial door size but again there is no reference in previous guidance to 6'6. ADB 5.16 does mention ceilings on escape routes to be no less than 2m and doors can be lower but again not specific reference to the actual minimum height of a fire exit. 

A lot will depend on where the door is and who would be using it, doors that are of a height that make them more of a hatch (often present as a legacy measure in older buildings as the only way to provide an alternative route) can be accepted in certain limited situations.

I was really after any information on specific recognised guidance or ACoP that specifies the minimum height of a fire exit.

There isn't specifically, the International Residential Code specifies that the primary (front) door in the home must be at least 80 inches tall (2.03m) and this is recommended in other situations, generally you see doors no less than 1.9m, but there's far less detail than on widths.

As a matter of interest, the minimum standard dimensions for a fire escape roof window (as opposed to a door) are 660mm by 1180mm.

 for use in England ... Doors on escape routes ... 3.6 Refuges should be a minimum of 900mm 1400mm in size and accessible

A Refuge isn't a door - those are floor area measurements!

Escape windows are not allowed in commercial premises - purely for residential premises. An escape window is completely different to a fire exit.

They do exist as a legacy measure in older buildings though, the usual guidance is a maximum of 5 staff only to resort to such. You can't use them in anything new of course.