Chris Lomax rings Directory Enquiries to obtain the phone number for Putapac Ltd (whose name he doesn't need to spell, curiously). He has already seen their transport, however, which all prominently display the number as 997 80811. It's conceivable he really wants the address, but as it's only Chilford Green Road, Chilford it would seem he'd be able to trace it easily enough (he lives and works at Chilford Green Aerodrome, suggesting it's not a massive locale.)