VPN, they don’t make you anonymous but they do encrypt your data between your machine(s) and your ISP so the ISP can no longer see (and record) every site you visit and the sites you do visit don’t know the ISP you’re using. IVPN and Mullvad are both good.
Switch your email to a privacy friendly alternative like Tutanota, Startmail, Mailbox or Proton, especially one that lets you have aliases.
Use Firefox (or even better, LibreWolf) with Containers enabled. If you set up a (for example) FB Container you could use FB in a contained tab secure in the knowledge any data it leaves on your machine can’t escape the Container. Also install UBO extension to prevent tracking.
Switch to a privacy respecting search engine - best of all are self hosted instances of SearX or Whoogle but, failing that, DDG and StartPage are both good.
If you use cloud storage, change from Dropbox/GDrive etc to something like Filen or Proton.
If you can, use Signal for chats. I say ‘if you can’ because obviously it means trying to persuade all your family/friends to use it too.
If you use Android, degoogle your mobile as much as possible, try and ditch as many corporate controlled apps as possible, use open source alternatives, avoid the Play store etc.
Hi fellow Brit :)