Sadly that shows how little you know about how the system works.....if your in contact with London/Scottish info call Mayday on their frequency, within seconds your details will be relayed to D&D and help will be at hand........if you call blind on 121.5 the chances of being heard below 3000ft in certain parts of the UK may not be great! Even higher over parts of hostile Scotland.
Could you elaborate a bit more on how the receiving systems for the different stations are set up? I am just curious since I had always assumed that since D&D and London Info are in the same building they would have identical receiving power.