You need PL insurance and reference books "appropriate" to your scheme.
calibrated test equipment.
Proof of qualifications.
As you say the information pack they refer you to does not exist. Try ringing and ask them to send the CPS information pack they state is available!
For other schemes you need BS1671, OSG, Guide to EAWR, Part P approved document, GS38.
Qualification certificates (normally just C&G 2382 17th Ed), PL certificates, health and safety policy, possibly waste policy.
Jobs sufficient to demonstrate your competence in testing and installation, preferably largish.
Knowledge of the building regulation requirements (Elecs guide to Building regs helps here).