2004 Vauxhall Astra brakes

I put the car into a garage to replace the seat belt, whilst it was there I had them look it to check for mot. They noticed that the pad retaining springs on both front tyres were snapped. They where replaced with new springs and when I drove away I noticed my brakes weren't the same. Before the garage the brakes where fine, but after I had to press further down before the brakes would work. My dad used to be a mechanic and he had a look and tried bleeding the brakes but nothing changed. We got advice and we were told that the master cylinder needs replacing. Me and my dad replaced the master cylinder and bled them properly but then the brakes where too hard, we had to stand on them to slow the car, and had to use handbrake to stop. We put the car into a garage, they had the car for a week, they refitted the master cylinder to make sure it was on properly, and they bled the whole system a few times and nothing changed. They then put another master cylinder on and bled the system again, the brakes now go all the way down to the floor and dont stop till the brakes hit the floor. The garage are out of ideas and I can't find any advice anywhere online.

I would appreciate any advice you can give please.

Thank you

Michael cobur