Rover used some cheapo plugs on the coolant system of the Classic that strip right off. The catch is these arent regular metric threads, you have to get british pipe thread. Which isnt so easy state side. Lucky for you I have a source for good quality brass replacment plugs. You need 2 for your system. I am selling them 2 for $30 shipped. Includes the gasket. Pm me your order. They also work on DII's where the diff drain plug is plastic.