i had the same problem with my drivers seat i think lots of people do. i took the seat out and removed the base fabric and covered all the foam with a new layer of 11/2 in foam which i used carpet spray glue to hold it in place. then replaced the fabric and replaced the seat. it took a bit of time but was worth it.
A tried and tested repair ^^^^ a bit like using new webbing to repair an old sofa that has a sagging seat cushion - oh for the days of being skint with rose tinted glasses.
I'm waiting for a dry day and time off work to look at my drivers seat as when pushing the clutch pedal down the underneath of my my thigh is bottoming out on the front edge of the seat before the clutch is fully home, I don't like toe flexure ! My Berlingo is a van with drivers and passenger seats different, passenger one is the fold down type.
Will update when I get it done.
Took both seats out this afternoon swapped over seat bases and spring supports and my drivers seat is now like brand new:lol::lol: really easy job
great job, hope my email helped lol