Direct Line use 0845 numbers elsewhere, so perhaps 0870 was used in this case because it can be called from abroad (all but expensively). Obviously no one told the department doing the website that calls to this number are more expensive than they claim (I suggest you make a complaint about this). In any case, the maximum cost of an 0845 number from a BT line is not 3p/min, but 3.95p/min for those few on 'non-discounted' tariffs like BT Light User Scheme. I notice that there is a toll free number for calling if you are in the US.
Anyway, to get back to finding a number for you, I have had a look at the DL site on
Internet Archive and this is what I've found:
This page lists, what appear to be contact numbers for customer services:
London 0181 680 2121 [now 020 86802121]
Birmingham 0121 616 2121
Glasgow 0141 226 2121
Leeds 0113 245 2121
Manchester 0161 839 2121
Bristol 0117 938 2121
Note how they all end with the same digits. I have noticed that other DL geographical numbers do this, so if you find a number for one office, you *may* be able to work out what it is at the others. Perhaps this goes back to the days when they used to use geographical numbers on their literature.
I think that we are looking for a pre-2000 number. However, it may be that the destination of the 0870 number has changed since then. Perhaps they do, or have in the past, sub-contracted out their 24 hour helpline. For example,
http://www.directline.com/travel/coverAnnual.htm]this page[/url] from 21/08/2001 shows the emergency contact numbers (with the same 0870) with a fax number 01243 773169.
Bear in mind that DL is now part of RBS, so they *may* have consolidated all 24 hour operations into one office. 0141 204 does seem to be used for RBS offices, see
Google results.