The ANO "Air Navigation Order" is the act of parliament that sets the top level of regulations in the UK. There's only the one, and it's not correct to refer to ANOs.
As with any country, the UK's general flying regs are in the AIP "Aeronautical Information Publication". In practice a proper understanding or UK air law needs both the ANO and AIP on the shelf. A company called AFE "Airplan Flight Equipment" publish both in one book called the UK AIM "Aeronautical Information Manual" for £15.
FARs are specific regulations about specific things, such as how to certify an airliner, or the required operating rules for an air taxi company.
In Europe, the equivelent of FARs are JARs, "Joint Aviation Regulations", which usually have the same number as the equivalent FAR - e.g. FAR 23 and JAR 23 both deal with certification standards for a light twin. In the UK, if there's an area where there isn't a JAR, then BCARs "British Civil Airworthiness Requirements" apply, such as for example BCAR Section T, Gyroplanes.
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