Just to clarify things a bit, the UK has had the "quadrantal rule" for ages, where a new FL was applied for every 90 degrees of heading. The UK was about the only country in the world which used this.
About a year or so ago EASA implemented SERA, the Standardised European Rules of the Air. SERA applies the semi-circular rule (FL based on headings that are 180 degrees apart, with different levels for VFR and IFR) across the whole of EASA-land, including the UK.
The textbooks and exams are now playing catch-up. Like they've been doing for the last five years when EASA has taken over various portions of aviation legislation.