If I am unable to find a geographical number, I will try and find there fax number. Fax numbers are almost always geographical numbers.What I do then is ring the fax number but change the last digit to one below or one above and somtimes but not always I get through. Sometimes you do not get through to the right department but they will usually put you through to the department you want, I just tell them I don't know how I got through to them and that I dialed the 0845 etc number. I recently did this with the claims department at NIG Insurance. As I pay a fixed amount to land line calls at all times the call does not cost anything.
Doesn't always work  but enough times to make it work ! ;)