I decided a while ago that it would be a good idea if I were to replace both my master cylinders and clutch slave cylinder, since for a while now I have had a leak which had been coming from the top of the drivers foot well.
So, I rang DSN Classics and asked for the bits I needed and the guy was hugely helpful. He old me that since my Mini was made in 1983 then I have a type 2 tandem brake master cylinder, which are no longer available, so the guy kindly suggested upgrading to a type 3 tandem master cylinder, which cost a bit, but worth it. The main difference (and the way to tell them apart) is if the brake level tester connections are on the cap then its type 3, also, if the unions which go from the master cylinder to the pressure-reg valve are the same size then it is a type 2, since type 3 tandem master cylinder’s have different size unions (10mm and 13mm I believe).
Anyway, that aside replacing both master cylinders was very simple and easy to do. The Haynes manual covers this particularly well, so I won’t go into detail. If you are upgrading from type 2 to type 3 master cylinder though, remember that you will require different brake pipes to connect to the pressure regulator valve. DSN Classics reminded me of this on the phone, again being extremely helpful.