Some UK HF Trading receive sites have been identified by a search of planning applications in the vicinity of the London data centre located in Slough. The ones shown in bold have antennas that can be seen on Google Earth.
51.569786 , -0.61712269 Raft Technologies / Ratesu Limited Beam on 30m Mast (retrospective)
51.569687 , -0.61714011 Raft Technologies / Ratesu Limited Beam on 30m Mast
51.523818 , -0.68828198 Raft Technologies / Ratesu Limited Beam on 30m Mast (refused)
51.456241 , -0.72476334 Raft Technologies / Ratesu Limited Beam on 30m Mast (refused)
51.565688 , -0.92764361 New Line Networks 8 Loops (Temporary now gone )
51.656720 , -1.0345119 Elecomm Wire V Beam (refused)
51.636671 , -0.96815008 Elecomm Single Yagi (gone)
51.636671 , -0.96815008 Elecomm 2 x StepIR beams on tower
51.665376 , -1.0496111 AM Nixey 8 Poles (none seen)
51.525498 , -0.52678395 Vigilant Global - Peter O'Hara 8 Loops & Beam
51.535552 , -0.79647021 BTS Data 8 Loops (gone)
51.534485 , -0.80112645 New Line Networks 8 Loops
I would think that there are similar sites around Frankfurt in Germany, but these have not yet been found.