2019 Ford Focus failed emissions 2019 ford focus 1.0 eco boost st line

Hi, 

Has anyone had a problem with a failed emissions test? We have got a 69 plate ford focus eco boost which failed MOT due to emissions after fighting ford as they said we needed a new CAT, Lookers finally found that there was a PCM update required - this was done and and the car passed. Move forward 4 months and the engine management light flickered on and off, with this we decided to do a free emissions test with Halfords and have found that the car emissions had started increasing again and only just scraping passed the test - it failed fast idle. Ford are saying they won't even discuss the issue again until we pay for another diagnostic test. - Any advice would be appreciated - Thank you