Welcome to the forum.

I have found a fax number

0151 934 7139

Email address  pensions.customerservices@homeoffice.gsi.gov.uk

I found that information here

http://www.civilservice.gov.uk/my-civil-service/pensions/help/home-office.aspx

So, at least you can fax them using a geogrphical number or email them

Hope this helps

Thanks guys. Without saying too much, I've dealt with various civil service departments for years, this one included, and have used the contact details you've mentioned - and they do work. However, no-one, even from that office, seems keen to disclose any alternative phone number.
Guess it's a case that they can "ignore" fax & email 'till it suits, but a phone call is more direct. 0845's being a way to discourage those... 
Thanks again guys, but I'll just keep lookin.