Pulled the glovebox out to get a better look and there appears to be a nylon flange which is wet on the right by the tunnel/firewall. There is a captive nut in it that you can see but i couldn't feel any head to the screw. The thing appears to go thru the firewall at that point and looks like it might come out behind the left cylinder head ( oh wonderful 
) My question is can the stuff under there (which i assume is the heater /air con) be reasonably removed to get more access without pulling the bloody engine out?? Appreciate any help 
Cheers
Wayne
Soooo.. it will either fix it or make it worse. Fingers crossed. Thanks again
The heater looked to be in three sections behind the glovebox and the middle bit looked like it would slide straight out. After undoing the tree nuts and two wiring plugs it did move out about 20mm. Then it stopped..... mmmmmm ,checked under the hood where there are two hoses. Gave one a bit of a wiggle and guess what .... yep plastic pipe it was attached to broke off. Unfortunately it wasn't the one attached to the bit of heater that moved. F@#K. Now i need some extra long pliers, ( you know- the ones you've seen in Super cheap and thought i could do with those. 
) to get at the spring clips down the back of the head. Even if i get the section out i might not be able to get a replacement part 
