Wouldn't it be a good idea to ask Revenue and Customs to publish a web page with a complete list of geog nos?
Has anyone ever done this?
I have found a couple of pages with limited geog nos, which are http://www.hmrc.gov.uk/workingtogether/prioritylines.htm and http://www.hmrc.gov.uk/workingtogether/ad_detail2.htm but the one I want is inevitably not there.
When I ask them for a geog no., they almost ask me what I am talking about, and I have never yet got them to provide one!

See also the one that we list in our database - www.inlandrevenue.gov.uk/workingtogether/ad_detail2.htm