I know this seems a bit of a daft question, but have you actually visited the office and tried to make an appointment? I have done this with my local tax office in the past.
When I type in Southport in the HM Customs and Revenue web site it shows this
The Triad
Stanley Road
Bootle
L75 1HW
If you're calling from abroad please telephone: +44 151 471 8435
Fax: 0151 300 1593
Is this anywhere near? If it is, dial 141 before dialling the number (obviously you will have to put a 0 infront of the 151) and make an appointment.
I do like the first line of this addrss, very apt!!!
Best I can do I am afraid, others may be a bit more successful. By the way have you got the post code for the Southport office?