Mac mini M4 Pro showing wrong date and time

Since switching broadband provider, Virginmedia to Vodafone, I have gotten this problem where Date and Time seems to be stuck on Pacific Daylight Time with the closest city as Cupertino. This is a pain as I live in the UK, so it's wrong. There seems to be no way to choose anything else as they are the only options. I have tried loads of things suggested by the internet, but so far nothing has managed to 'unstick' it. Location Services etc, etc. The IP is showing as London but time still in CA. Any helpful suggestions?