SafeSearch is a service provided by Google. Either you have activated the service on your Google Account or Sky Broadband is using the service for their users. If it is from Sky, then you will need to contact them to turn the service off for your connection. It is not a service provided by Apple or would be installed by OS 18.2. More information about SafeSearch is here:
https://support.google.com/websearch/thread/275838697/my-safesearch-is-locked-on-my-ipad?hl=en
If you are using a VPN or there is a management profile installed, you will find that at Settings > General > VPN & Device Management.