There is an official protocol in place in the event of the death of Her Majesty the Queen, officially known as 'Operation London Bridge'. It covers the activities for each day from when the Royal death is announced (Day 0) through to Day+10 when the state funeral will take place.
The Central Council of Church Bell Ringers has issued guidance in accordance with the official protocol. This may be viewed using the links below:
Guidance Note: Operation London Bridge (webpage)
Guidance Note: Operation London Bridge (pdf file for printing and electronic distribution)
The key message is that ringers/towers should liaise closely with church authorities to ensure that appropriate ringing takes place.