Braking issues

Good day,

I have a leyland mini 1275, I purchased the vehicle recently and after two days of use, when pressing the brake pedal down, it would lose pressure and brakes would not work. I assumed this was a master cylinder issue and after no success myself I then took it in for repairs, they said it needs to be replaced. Now unfortunately I cannot find a new master cylinder here in south africa, I managed to get hold of an opel corsa 1.4i master cylinder which will be able to work in the mini as far as I can tell, however when the piston in the master cylinder is pushed in, fluid leaks out the bottom, I dont know how a opels master cylinder works so I am not sure if this is normal or not, if so I guess it wont work on the mini.

Is there any other solution, or master cylinder that could replace my old one?

Michael