All foreigners coming to canada have to obtain a visitor's visa before entering. You can apply for it online before you travel - it takes only a few minutes and costs 5 quid or something like that.
You can use your regular British driver's licence to hire and drive a rental car.
And I'm sorry to report that most major liquor stores in Ontario (which are government controlled) are closed at the moment due to strike action. They might reopen 19 July but unclear.