Standard ST valve springs are ok as long as you're not chasing crazy revs.

Piper can reprofile the inlet cam and supply new valve springs and retainers if you do want to rev it out more.

To disable the VVT you need to tap the oil feed and put a grub screw in.

You'll also need to turn up an adaptor on a lathe to run a 2.0 Zetec vernier on the end of the inlet cam.