All ACC's have to monitor 121.5MHz as it is an ICAO requirement. For both London and Scottish FIR's this is done on NATS behalf by London and Scottish Mil. Both civil centres have the capability to select 121.5 MHz when required.
Can't speak for Swanwick (or Manchester or TC), but there is no capability to select 121.5 in the civil part of Scottish ACC, except in the engineering domain.