Peugeot 206 (207 reg)?

Changed my pads discs on my Peugeot 206 (207 reg), but didn't make much difference, however, during the following weeks, though the car 'stopped', the brake pedal slowly got more 'spungy' and was much lower to the floor, before the brakes fully engaged.
As I wasn't losing any brake fluid, thought that the internal seals on the master cylinder were letting pressure 'through', so had it changed, (using best parts), however, even though the brakes were fully 'bled', I still have the same problem. So I would be grateful , for any 'professional' help / ideas
Thank you...