Well, I've partially answered my own question having a donor scrap 2002 tourer and the 2005 tourer to play with.
The 2005 has the space for a tailgate/boot remote opening switch covered by a blanking plate.
I removed the switch/plug and a section of loom from the 2002, removed the kick panel on the 2005 hoping to see a spare blue plug, which has two wires, one black which is a ground, the other pink/grey, no luck, so looked for the pink grey in the loom, there isn't one, more than likely due to it no longer being an option on the facelift.
So if I get a bit of time I may get eye strain going through wiring diagrams, in the mean time if anyone need one of these switches, you know where it is.