A brake controller is a device that is fitted to your car to control the brakes on a trailer. It makes sure that your car brakes and the trailer brakes are applied at the same rate so that when you are going down a hill the trailer doesn't push the car along.
A brake controller is not a standard accessory and is fitted by a mechanic.
It’s not a legal requirement to have a brake controller when towing caravans over 750kg. Caravans over 750kg must be fitted by law with overrun brakes.
Alternative options if you don't feel comfortable to drive such a heavy vehicle:
Find a camper trailer under 750kg to hire.
Find a motorhome/camper van to hire.
Find an owner that will drop off their caravan at your required destination so you don't have to tow.