That's a good point and I probably should have mentioned that after you get the parts unfrozen you would have to assess whether you now have a disassembled master cylinder that can still be used with some new parts or if you have a disassembled master cylinder that is garbage.
I should have also mentioned that Dietmar at Quixote Racing (
http://www.quixoteracing.com) only has Wilwood cylinders on his parts list but I would consider giving him a call. He might have Girling stuff also and he has been an incredible source of information and help for me.