As found on service sheets 363 for sound version and sheet 278 for various others.
Hornby Genuine Spares X9911 Railroad Class 9F Chassis Bottom & Pickups Contacts
Hornby Genuine Spares R30049/08 Chassis Frame For Class 55 Loco R30049
Hornby Genuine Spares X9973 Underframe Chassis For Class 153 DMU For R2759 NEW