TB2 - bummer about the master cylinder Scott! Make sure if it has ABS the new one is suitable for ABS (ditto if it doesn't have ABS, the master cylinders are different) and as it seems to have gone suddenly suggesting water contamination, it might pay to flush the entire braking system with meths before adding the new fluid.
Also might pay to invest a few quid in one of these :
https://www.ebay.co.uk/itm/Brake-Fluid- ... 4396159192
I bought one, tested my Volvo, 1-2% depending exactly where i tried it. It went berserk in the Sterling so that's another job when i get the Sterling back again!
Don't forget to slacken the handbrake cable off before removing the rear pads and only readjust it after the pistons have been wound all the way back in, pads fitted and footbrake operated several times until the auto-adjusters stop ratcheting. It worries me when you say "when you get TB2 back" - does that mean someone else is fitting the rear pads, discs and master cylinder?
Vitesse - remove the two trim panels in the boot on the inside of the rear wings and find the sunroof drains. I'd lay bets they aren't watertight! Also inspect the seam on the channel next to the boot lid seal, it's at the screen end of the channel each side and lets water in, quite a sneaky one and if you don't realise then you could end up with the same as my Sterling has just had repaired, rear ends of the sills and on one side, trailing arm mounting point going rotten.
Fingers crossed on 2021 being better! Happy Xmas and New Year to you and your family Scott!
