Remove the whole filler cap 3 fasteners hold the flip part down then several 2mm grub screws hold the main part in place.

just like in my reply to your PM
If the mounting flange for the filler cap hasn't been out for a while it can be a stubborn

Remove the cap (3 x allen screws), slacken off the grub screws round the cap housing, lift off the housing (pull off the overflow hose), slacken the hose clamps, remove filter. Unless you have small hands and nimble fingers, you might find it easier to remove the pump and filter together and then split them.

oops - sorry - missed the page 2 replies