MK3 Focus brake went spongy but still kinda works

To anyone out there who knows a lot about focus' specifically and their known faults, can you point me in the direction of what might be wrong?

So i was on my way to work and half way there my brake started feeling off, i had a deadzone that went like 3cm with a whooshing or air pressure noise where nothing happened, then after that i finally got some force from the pedal and the brakes started applying. I tried pumping the brake with the car on, no change, with the car off it goes stiff like normal. Ive taken it to my local garage and they dont seem to think anything is wrong with it so im going to take it to my local ford garage when i get a chance, anyone know any specific problem that it could be, if its a known fault, its a 1 litre ecoboost on around 60k miles