I’m quarantine ?

Do you really need the police to make sure you’re acting like a responsible human?

And for the record, quarantine means you don’t go ANYWHERE except for emergency medical care.

I'm not in the UK but as far as I know they don't. You're responsible for your health. If you're quarantining then you should be at home. Only go out for groceries or medications, if you have to go out wear a mask when you're in side places like grocery stores or malls, even public transit in your area may require you to wear a mask. I don't know if this is true, but I've heard in China they were nailing doors shut.

That varies per place but if your quarantine definitely stay inside because if you violated and get someone sick you could be responsible for their death and they could spread it to other people who die in the guilt goes back on you