More specifically:
Height sufficient for recovery by 3000ft agl;
Location: Clear of cloud, built up areas, aerodromes and controlled airspace;
Lookout: Clearing turns 180 degrees left and right to check for other traffic in the vicinity level with and above and below the aircraft.
But even for steep turns the clearing turns are taught as UK airspace can be quite congested at times and it is regarded as good airmanship point an essential safety point.
Training areas in Northern England at least are often fairly restricted in both vertical and horizontal extent and used by light aircraft and micolights. I've had some encounters closer than anticipated even with a good lookout so the clearing turn procedure is taught even though steep turns in themselves may not be a particularly demanding exercise in terms of airspace requirement or aircraft handling.
KR
FOK