JAR-FCL is a guidance document, adopted in their own way by different companies. (And occasionally by different people in the CAA, depending upon how they feel that day). Textbooks get out of date too.
The definitive document is the UK AIP. You can find it online, or spend £15 and buy AFE's UK AIM, which includes the AIP. ANO and some useful AICs as well. The AFE copy obviously only gets updated yearly, but that's usually good enough.
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