Fiesta 2010 brake issues

Hi,

I have a 2010 Fiesta, up until recently it’s been the most reliable little car possible. 

Randomly, when I go to brake, the pedal goes really soft and I have to put my foot fully to the floor for it to be responsive and brake. If I feel it’s happening, I take my foot off of the brake and brake again, it’s responsive with the lightest touch and brakes! It’s been happening since maybe late October/early November. 

Consulted google, it’s a known problem (although I didn’t do this straight away)

I’ve taken it to 3 garages now. A Kwik Fit, Formula One and a local garage to my area that have a very good reputation.

Kwik Fit replaced one set of discs, said they checked my brakes but didn’t test drive it and said everything seems fine... issue still happened afterwards. Took it back to them and they said they would re check, but it still happened.

Formula One bled my brakes, changed the brake fluid and said see how I get on, they spoke about replacing the shoes and some rear cylinders if it doesn’t stop... it carried on. 

Took it to a local garage through a recommendation as formula one are hit and miss with their reviews, they changed the shoes, cylinders and bled the brakes, they said they’re familiar with the issue and said sometimes they have to replace the master cylinder also. Same thing happened when I was driving home (probably a 10 minute drive) so went in to see them again next day and they said the fact it goes soft makes them think it’s trapped air not the master cylinder, but see how it goes, it might just be the air getting out the system after they carried out the work. It still happens.

Can anyone make a suggestion of what to do next? Currently this issue has cost me about £650 to try and sort with no luck. Ideally I don’t want to take it to Ford as they’re the more expensive option. I think the car is only worth around £2,000 max! 😅 

Any help or suggestions would be greatly appreciated. 🙂