As en-route controllers in the UK we don't normally have access to 121.5 to either receive or transmit. We need to speak to D&D who can either do it for us or they can release the frequency to us for a bit.
If there's something really bad, it might be worth letting the main frequency know if there's time or RT space and we can let D&D know, although I guess they can hear it just as easily as you can