Upvc window trims

[Spreadsheetman]

In my current renovation project there are some old upvc windows and it looks to me like the internal quadrant trims and strips are hiding various sins that I need to fix (with expanding foam probably).
 

I’ve never removed or fitted these trims - how do you get them off and how (and with what) do you stick new ones on again?

[Sparrowhawk]

On my windows the trim strips are glued and caulked into place. My approach is to use a Stanley knife to cut through the caulk (trying ever so hard not to slip and cut the UPVC window frame) and then get a scraper underneath or even a chisel to loosen an end. After that the whole strip can often be ben upwards and the now-brittle glue breaks.

 

If you need new ones (can you fix it so they're no longer required?), my approach has to been to stick them with caulk or silicone sealent in place. Easier to remove next time!