Aero, in UK we don't have "hemispherical" levels. We do have quadrantal levels for lower airspace but they don't start until above 3,000 ft.
In the London area (i.e. much of the south east of UK) there is Class A airspace at 2,500 feet, so quadrantals cannot be used.
See and be seen / bunfight at busy periods is the rule!