ICAO FPL convention is that lat/long uses the following format:
Degrees and minutes (11 characters):
4 figures describing latitude in degrees, tens and units of minutes followed by ‘N’ or ‘S’, followed by 5 figures describing longitude in degrees, tens and units of minutes, followed by ‘E’ or ‘W’. Make up the correct number of figures, where necessary, by insertion of zeros, eg 4620N07805W.
However, NOTAMs are often written thus:
NO ACFT IS TO FLY BELOW THE NOTIFIED BASE LEVEL OF CONTROLLED AIRSPACE WI THE AREA BOUNDED BY STRAIGHT LINES JOINING SUCCESSIVELY THE FOLLOWING POINTS: 513540N 0002816E - 513424N 0001906E - 514508N 0001309E - 515828N 0003314E - 515924N 0004119E - 515450N 0004712E - 514408N 0003049E - 513540N 0002816E
By inspection, it seems that these are DD:MM:SS values rather than DD:MM.
The UK AIP uses a mix of DD:MM:SS and DD:MM.m values.
Surely it is time to standardise on one system? Quite why a NOTAM needs to include values to the nearest second is beyond me - if DD:MM is good enough for FPLs, then why not for NOTAMs?
At least one military friendly fire incident was probably caused by DD:MM:SS being entered as DD:MM.mm; although nothing quite so problematic is likely from similar misplotting of a UK NOTAM, the lack of clear identification of units does not help.