Rear Seat Belt Top Brackets

Hi, I'm fitting my folding rear seats (forward facing to replace the old side facing) and unsure of the best way to finish the trim around the monstrous top mounting brackets.

They fit, but some significant cutting is going to be required and I wondered if anyone with the same set up could share a picture please?

The trim sticks out around 20mm due to the (massively over engineered) bracket now in place.

...also, any idea what the 4x M8 nuts, 1x M8 top hat, 2x plastic and 4x stainless washers are for? No instructions whatsoever and other than 1 existing nut there are no M8 fixings in the area?!