Ok, with regard to frequencies over Caterham Surrey as requested. I imagine this is a very busy area for air traffic. You are directly underneath the London 'Biggin' sector (120.525MHz). This extends from surface to FL175 and handles traffic inbound to Heathrow from the South West, this traffic heads straight for Biggin where it is either passed to Heathrow director on 134.975MHz or is held in the Biggin 'stack' when its busy. The sector also handles Gatwick departures heading East & North and Luton, London City & Stansted departures which are routed to the East of Heathrow heading South/South West.
Above this, are Vaton up to FL215 (127.95MHz) then S26 upto FL305 (132.6MHz) and finally S2 upto FL660 (127.425MHz). As with other frequencies some of these may be bandboxed together during quiet periods.