Front Door Discolouration Problem

[JamesS01]

About 10 years ago I had UPVC doors & windows installed with the front door being a Paladin composite unit. The glazing retaining trims have become severely yellowed on the outside - the inside ones are fine (see attached pictures). I cannot trace Paladin so it seems they may have gone under & I'm not getting much joy from the installers so can anyone advise if it's possible to return the trims strips to their original white colour? Ordinary household chemicals including bleach don't do anything

 

[Gazman16]

Hello
They are called glazing cassettes and can be replaced.
If its under 10 years old and still in guarantee I would persevere with your supplier/fitter. Maybe start hounding them on their social media sites.
If out of guarantee then they can be a little tricky if you don't know what your doing.

If you want to have a crack at it your self look on the inside cassettes for any little plugs that cover screws, If you have those its fairly simple. If not they may be more complex ones

 

[JamesS01]

Hello
They are called glazing cassettes and can be replaced.
If its under 10 years old and still in guarantee I would persevere with your supplier/fitter. Maybe start hounding them on their social media sites.
If out of guarantee then they can be a little tricky if you don't know what your doing.

If you want to have a crack at it your self look on the inside cassettes for any little plugs that cover screws, If you have those its fairly simple. If not they may be more complex ones

Yes, the plugs are there but I'm not sure I can get them out without marking or damaging them. Do you think I can just swap the inside ones for those on the outside?