Thames Radar is only on 132.7. 119.9 is Heathrow Special (VFR) and would normally be used for low-level SVFR transits on Western routes like the famous Ascot-Burnham corridor.
In reality Thames and Heathrow sit next to one another at the bottom of Heathrow's Control tower.
Certain of Thames Radar's controllers are also of the view that since they are not a LARS unit, they should not provide services to aircraft outside controlled airspace. For them this means that their priorities are Biggin Hill IFR in and out-bounds and City Airport traffic.