I found a document online intended to instruct police officers on how to deal with drone offenders (pretty much of all the drone users). Here is the list of few interesting extracts:
The ownership and use of drones are not of themselves unlawful but in certain circumstances, their use may contravene air safety legislation or other statutes, commonly used to manage other types of offending. The intention of this guidance is to address the negligent, reckless or malicious use of this technology.
It is not the intention of the Police Service to criminalise innocent misuse and the criminal justice system provides options for non-recordable disposal. However, some innocent misuse might also be reckless and therefore Appendix Two to the SOP provides a gravity factor matrix that users of this SOP may use to help them in decision making.
There is no power of seizure with the Air Navigation Order 2009 offences. Consider S19 PACE if on premises or Common Law (protection of the public – stated case now includes misdemeanour offences). If other offences have been committed or you make an arrest. Consider powers of seizure under these statutes.
Important: Section 43 does not prohibit the taking of photographs, film or digital images in a public place and members of the public and the press should not be prevented from doing so in the exercise of the powers conferred by Section 43.
Officers should not attempt to take control of the system UNLESS EXCEPTIONAL CIRCUMSTANCES EXIST, such as a threat to life or injury or damage to property.
Note that there are no specific powers of arrest or seizure in relation to offences committed under the Air Navigation Order.
What can I do to stop a drone once it is in the air?
Currently, the only option open to you is to instruct the pilot to land the drone.
Can I seize UAS that are used to commit offences?
There is no power of seizure of the Air Navigation Order 2009, but you could consider s. 19 PACE 1984 or common law powers. If a UAS is used in other offences, or you arrest people, you could consider using powers of seizure under those statutes.
Can I view footage taken by drone?
No, not unless you reasonably suspect the person is a terrorist in which case you can use powers under S43 of the Terrorism Act 2000.
Here is the link to the original document