Might be worth checking youve got the correct phone aerial loom in there before you go too mad. 
Any pointers as to how I do that?
Drivers Footwell (A Pillar is probably a good place to start), what your looking for is three
coax cables, FM Radio, Probably Grey, thicker of the three cables, that will be there, GPS, probably Black, a thinner Black cable, that should be there if its a late Elite, and a GSM again probably Black thinner cable, may not be there, but might be if late Elite.
Some or all of the cables above maybe wrapped in a foam covering but the loom has connectors at the footwell which breaks the loom from the HU / Telematics to the footwell / the Aerial Loom, on the Estate, all three cables run to the Aerial Base / Whip on the Roof. You can get access to the Roof Aerial by partially dropping some of the rear Headlining.
You could also compare the cables from the donor car if it has Telematics fitted, at the A pillar foot well guessing the cable set up here should be the same whether Saloon or Estate, unless someone knows otherwise.