Without taking the calipers apart, I can't really see what the pistons are like. The piston dust seals are in good condition on both sides. There are no visible leaks around the servo or master cylinder. One thing I did notic is that I bled the front brakes a month or two back and since then the pedal has gone quite soft.
Whats the best course of action? I realise that it could be the servo, the servo rod, master cylinder, brake flexihoses or the calipers themselves. Is there any way to exclude some of these or is it a case of replacing everything until they are sorted?