I don't think SERA applies because the UK CAA have seen fit to exempt us from many of its Rules, to our benefit, it seems.
As I understand it, the semicircular rule only applies above 3,000' (not forgetting that the lower flight levels aren't available in times of high atmospheric pressure).
Afraid not - see
http://www.caa.co.uk/docs/2884/20150...solidation.pdf - it states:
That states:
3) SERA.5025(a) (IFR - Rules Applicable to IFR flights outside controlled airspace)
For the purpose of SERA.5025(a), an aircraft in level flight outside controlled airspace at or below 3,000
feet above mean sea level and operated in accordance with the IFR is not required to be flown at a
cruising level appropriate to its magnetic track if it flies:
a) in conformity with the instructions of the appropriate air traffic service unit; or
b) in accordance with holding procedures notified in relation to an aerodrome.
Or to rephrase that, if not flying in conformity with the instructions of the appropriate ATC unit (if OCAS there likely isn't one), or a holding procedure, then it is required to be flown at a cruising level appropriate to its magnetic track - there's no blanket exemption below 3000'...