rear strut brace fitting and ver7 rear seat to classic

what a day

after a lot of fidling and swearing and struggling i have my original rear seat out of my car and my rear strut brace fitted

my question now is how do you dit the ver7 rear seat in a classic as im not 100% on this

any help would be great

do i leave the grey plastic trim behind the seat in or does that have to be removed ?

thanks