What should I do to be legally compliant?

Since January 1st, 2021 a new European drone legislation is applicable which makes it easier to fly small drones. 

For Belgium you can find all the information on this site of the government:

https://mobilit.belgium.be/nl/luchtvaart/drones/nieuwe_regelgeving

 

For the UK, you can find all the information on this government site:

https://register-drones.caa.co.uk/drone-code