it seems to have lost a little fluid but i can't see where from.
That, and all the other symptoms are classic master-cylinder failure.
If you've no obvious external brake fluid leaks, then it will be leaking into the servo.
It might be worth undoing the master-cylinder mounting bolts and seeing if you can move it enough to see into the servo to confirm this, before buying a new one. I'd be reasonably confident about buying a new cylinder without doing this.
Is it worth checking the servo pipe is fully connected and air tight.
And just wondering if the low level could be dropping naturally due to pad wear? Or is it more than that proportionately?
#
servo pipes seem fine, with the motor off the brakes will pump hard once the vacuum is used, the level seems to have dropped about a third, I don't know how proportionate that is? anyway i have another master cylinder now just need the time to do it!! probably won't be before next week now, will let you know how it goes! thanks for the replies.