A new Radisson hotel opened (is opening) in my town, so I tried to check availability. 10 mins later I get an email from Premier Inn asking if I was looking for accommodation in my area!
The browser you're using, knows you looked at that site, it also knows your geographical location (based on your IP address), and because you're logged into your browser, they have your email address already.
You can use ad blockers all day long, but that will not stop these types of emails.