The armrest unit from VW is £210 without the harness or device cable, the device cable from VW is nearly £40,
I use partsdealer123 now again and they are usually good but sometime can send damaged units out so if they do just tell them and they will swap it without question...they do try it on with damaged units.
VW actually do do a retro hraness so you can keep the aux if you have that already.
Cheers
Darren