The location of the Epsom NDB 'EPM' (freq 316 kHz) is the same today as it was in 1969 (chart shown below), approx 5 statute miles WSW of the centre of Epsom town, but I don't know its history prior to that. EPM is the holding pattern for aircraft to proceed to after missed approaches from LHR runway 09R/27L.
ILS chart R27L