Would appreciate any advice on removing the door mirror trim please?

 

From that picture it looks like you just grab the old one and pull it out - removing the actual mirror glass first would make that possible/easier, and to do that, you need to tilt the mirror fully one way and ease the glass out, it is mounted on a plastic holder by the plastic bonded onto the rear of it.

 

That advice comes from common sense and dealing with a later version of VW Group car mirror.

Glass out first makes it easier but take care not to break it! The glass will pop off if you place a plastic prise tool or similar behind it and gently lever. This then levers off those little clips. (Thats why its easier if the glass is out-more space). That part is called a "Bezel". Should cost around £10-£12 from the main dealer. (Often MUCH dearer when obtained elsewhere, surprisingly).

Thank you both for the info.
I ordered one from Ebay last night for £10.99 + £5 shipping.
Should have tried the dealer first but I was being impatient and pessimistic.

Fingers crossed I don't break the glass.

Follow the instructions on the attached file.

Awesome. Thank you very much for sharing that.