I had a small accident that has resulted in a cracked plastic trim.

Only thing is, I don't know what it is called to try and find a replacement!!

It is the plastic part on the rear of an Octavia hatch that runs above the numberplate and is body coloured.

What is this called:D

The same part can be referred to by different names from different people. Your best bet is to describe where it is, on the inside or outside of the car, what it does, made of and any components that are attached to it.

From what you say you are after the exterior plastic trim above the rear number plate, that requires painting and it houses the boot lock barrel.

I might call it the tailgate trim, or the lock mount, or the numberplate light mount, for example.