Brake pedal travel

Hey all,
Just changed brake pads on my wife's mkv golf and now have very long pedal travel. I have read this thread https://www.vwaudiforum.co.uk/forum/s...ead.php?t=3946
and many others but still no solution.
No fault codes as yet on VagCOM. The pedal sinks to the floor when the engine is off, probably same as others, just apply soft constant pressure and it will sink. Most people (including me at first) press too hard because lack of servo assistance, press hard and pedal doesn't move just like when engine is on.
May have screwed a seal up by pushing pistons back, but doubt I could damage seal on master cylinder, which seems to be confirmed by above post. I didn't open any valves so should be no air in it. ABS works so doubt I have damaged seal in there. The car has ESP if that makes difference.
Going to mechanic on Thursday but from other posts doubt if it will help besides noticing something silly I done and can't see.
Anyone any advise? Seems to be a few posts on this across the VAG range but with no real solution, would be great to find one!
Thanks

With engine off when applying pressure smartly to the pedal you say it is firm,if you then start the engine do you feel the pedal drop slightly?As this will indicate servo is operating correctly.
Could you let me know.

Jeff