The military maps unless specially ordered (not sure if they are available anymore) is the civilian map! I dont use stuff as small scale as 50 000 anymore but map down to 1 in 5000 or less using an OS online system.
Are you after the map number, series and latest issue date? If so it will be OS online. I'll check details now.
In fact the os online offers you the military trg area or the village as zoom in options!
1 in 50 000 is map 160 of the Landranger series.
1 in 25 000 is either 188 or 200 I think on the Explorer series.
I rarely buy maps now as the land survey work I do now requires much more detail.
Series GSGS 5294
Edition ? (4-GSGS is 1996)
As the man said, the 1:50,000 OS map is sheet 160.
As for 1:25,000, the OS Explorer OL12 covers the Beacons (as far N as the A40 through Sennybridge) - I think sheets 187 and 188 would cover the area, but if you're sticking to the trg area, I would keep to the SENTA map above.