hi everyone
ive got a 2010 mk2 focus, and the other day the passenger side door handle came off.
now the door handle fits back on perfectly, but the plastic trim bit to its right wont stay in.
i have replaced this peice as could see some of the lugs had broke, but still having problems getting it to fit

Any advice?

It is not possible to repair it. You will have to change the knob. I also faced the same problem and I have to change it entirely.