Correct me if I am wrong but doesn't the UK ANO already prohibit a flight crew member to be paid for his services with a non UK licence in Section 1 Part 6?
That part applies to G-registered aircraft. There's nothing in the ANO that stops a foreign-registered aircraft operating in the UK with a paid crew that hold licences from the state of registry only.
Of course, the operation they are allowed to perform is restricted to the rules of their own registry (eg. private vs commerical/PT) and the UK rules (eg. a US Part 135 operator can't offer air taxi within the UK).
Under EASA, if the operator is EU resident, any crew (private or paid) will have to have EASA FCL licences (although they may continue to operate a foreign-registered aircraft in the EU with relatively few other hassles).
brgds
421C