Brake fluid leak

[chrish]

In searching for my mystery brake fluid leak I found some sticky liquid (yellow brown colour) on the inside rim of the offside wheel. The brake lines and calipers are dry enough. There is a little grease under the hub carrier, as most Griffs suffer from. Could this be it or just grease?
(Thought I might find some brake fluid inside the clutch inspection hatch or under the pedals but dry as a bone)
Got to be the servo itself then?
Chris