Items below are what I used when replacing arch liner fasteners on my Trophy. Can be seen on my old Trophy project thread (a lot of people messaged me last year asking where I got the fixings from after viewing my thread).
Screws:
https://www.accu.co.uk/en/self-tapping-hexalobular-torx-pan-screws/22370-SHPT-No-8-3-4-A4
Washers:
https://www.accu.co.uk/en/flat-washers/14681-HYW-M4-12-A4
For the washers, up to you if you want larger than 12mm diameter. For the back they are perfect, on the front you might want slightly larger diameter, say 15-17mm ish or so, otherwise the same specs. I seem to remember I bought a few of each (12mm, 15mm, 17mm) so I could choose.
And I know you haven't asked about these, but if anybody wants new clips/fasteners for the front bumper where it meets the wing, you want these (M6 spec).