Had a couple of emails from Tim at http://circuitsupplies.com/
The price for the DS2500 pads is £84.10 plus VAT, which seems pretty good to me. So I've ordered a set. He's checking availability wth the factory. But he hasn't given me the part number yet.
He also said that
part numbers starting "FDS" refers to Ferodo "DS
Performance" pads. These are a fast road pad only, and made within the confines
of a regulation called R90.This states that these pads are, amongst other
things, within plus/minus 15% performance of the OE pad for that particular
DS2500 on the other hand, is outside the scope of R90, and is approx 40% better
than OE pads. It is designed for "track day" use.
DS2500 should not be used on road cars, registered from 2000 onwards.
The exceptions to this, is where it is used in a brake upgrade,IE DS2500 is
supplied in all AP Racing "Formula" brake kits, as AP have found it to be the
best pad, for this application.