Technically - yes. Owning and/or using a scanner is not illegal - providing you're only using it to listen to transmissions meant for public broadcast. You are only legally allowed to listen to anything that's meant for general broadcast. That covers things like AM/FM radio, TV audio, shortwave, CB and Amateur radio.

In the United Kingdom, it is technically illegal under the Wireless Telegraphy Act 2006 to listen to radio transmissions that are not "intended for general reception" or for which you do not have a specific license. This includes Air Traffic Control (ATC), police, and emergency services frequencies. Unlike in the United States, where listening to ATC is a popular and legal hobby, the UK law considers these transmissions private. This is the primary reason why UK airports do not appear on popular streaming sites like LiveATC.net. However, the law is rarely enforced against passive "enthusiasts" using a handheld scanner for personal use at an airport perimeter, and scanners are widely sold in the UK. The legal "grey area" allows people to buy the equipment, but the act of listening remains a summary offense. It is strictly illegal to record and rebroadcast (stream) these transmissions online. To listen legally, you would technically need to be a pilot or a ground operator holding a Flight Radio Telephony Operator’s License (FRTOL).