Surely the CAA as guardians of Air Safety in UK airspace would have sufficient juristiction to ground an aircraft or indeed stop them flying in UK airspace should thery consider it unsafe to do so. Having Jeppies so many amendments behind may constitute a breach of safety.
They can ramp check any aircraft in the UK. But to stop them flying in UK airspace would require a lot more legal work and for the airline to be proven to be unsafe and added to the 'black list'.