Swarming is the natural method honeybee colonies use for reproduction. The original colony replaces the old queen, who leaves the hive with about half of the worker bees and as much honey as they can carry. Swarms land on a structure near their original hive location, cluster themselves, while scout bees leave in search of a new hive location. Once the scout bees return they convey their findings to the swarm, which is then followed by them departing for their new home.
Honeybees are at their most docile when swarming. At this stage, they do not have a hive with honey and brood to protect, and their honey-guts are full of honey stores from the original hive. Full bees are gentle bees, partly because it is physically difficult for them to tilt their abdomens enough to sting.
However that does not mean they will not defend themselves if threatened.
Keep people and pets at a safe distance from the swarm
Check the advice on the BBKA (British Beekeepers Association) website, they will help to identify the possible type of bees
Seek the advice of a local beekeeper, most will be happy to assist with their removal, if they are honey bees and in safe working location
It is important to note that your local beekeepers are only able to provide assistance (if and where possible), when it is a swarm of honey bees.