Shep, I measured the discs and they're slightly less than 12mm thick. I'm not sure what width they're meant to be, I'll have a google and see. They're rusty, but don't have any major grooves in them or anything.
And the springs are definitely mk2, both ~130mm dia, and both ~255 long.
The tanks. The one with no sender has some dents in the bottom of it, and looking inside it's got a bit of surface rust, but not too bad. The one with the sender in it is pretty well straight, but it has had a repair done on it. No idea about the rust in it cause I can't see in, but when shaking it there sounds like a lot of loose something in there. I have some more pics of the tanks, but they're on the camera still.