Many thanks to Dave, DaveM or bbb_uk for so rapidly verifying the entry added for the Passport & Identity Service for their
web callback service.
Although the web page for the callback service says it is only to do with calls about the online application form in reality queries about the online application form can be turned in to queries most people are likely to have about almost any aspect of applying for a Passport since the IPS only print out your completed online form and send it to you in the post for signature and the addition of a photo for you to then post back to them.
The number that called me back was a Bristol 0117 915 1900 number on my CLI but when dialled this is just an announcement message from Teleperformance apologising for the fact that they missed you when they called on behalf of a "blue chip" company and giving an address to email if you no longer wish to receive unsolicited calls from them on behalf of their clients.
So no wonder an 0870 number is being used by the IPS when the whole damned operation is clearly outsourced to Teleperformance and/or other similar third party call bureaux. It has to be said that the lady who called me back from Teleperformance on behalf of the IPS was quite bright and helpful (not my experience of other Teleperformance Call Centre staff acting for other companies) but she still needed to refer my question about why the IPS requires proof of non standard titles (eg Dr, Major, Sir, Lord etc) on Passport Application forms when the Passport itself does not have a Title field at all elsewhere (i.e. to the IPS itself although she did not admit this or that she worked for Teleperformance rather than the IPS).
I got the impression that not many people use the web callback service so far as it is rather well hidden on their site so heaven knows how Teleperformance and/or the IPS will react if they suddenly start getting a lot more web callback requests. But note that the callback I got was on a Saturday afternoon so you may find it convenient to make a web callback request in your office on Friday afternoon giving your home or mobile number for callback the following day.