I had my focus serviced (by a “professional garage”) and they got dirt in one of the o-rings. Push pedal and it just kept going. Pump and it got a bit firmer, but made a big puddle of brake fluid on the floor. Took it straight back and made sure it spilt the rest on their forecourt.
If you can get it to a point where you can really push on it hard and it wont move (i.e. full force you can do), then its probably not leaking, but I would go and get it checked – don’t p*** about with tyre and brakes, you want them to work when you need them.
My one does have a bit of squish when the power assist kicks in, but its not like you have to pump it many times (maybe an inch).