I used the technical section!

[Chix]

Thanks to Bob and his information on how to change the Master Brake Cylinder, really helpful, thanks!

I had to take the servo off to get the lower nut off, but it wasn't a big deal.

I think I will still do a full bleed though, as the fluid that came out of the Master Cylinder... well... let's just say some of it wasn't actually fluid...

[Roy_S]

I had the same issue with the lower nut on the master cylinder, could not physically get a socket on it, spanners did not give me enough movement to undo.
I did post the pictures on here, showed the old MC was slightly bigger casting, we're talking a mm, but enough to prevent a socket getting on it, the picture I posted showed the outline of the washer, you can see it goes right up to the cast body of the MC.
Could get a socket on the new MC.

[sujitroy]

Fortunately for LH drive stags, you don't need to remove the servo to take the brake master cylinder off.

[richardthestag]

The bottom nut has a bad name made up for it. I found using 1/4" drive 6 sided sockets and various extensions and bits I did manage to get it undone.

It was more fun than the RH exhaust manifold though.

Amazing how dirty the old fluid can get isn't it