I think any harness like that one will do the job, I've found a couple others here
http://www.ebay.co.uk/itm/1209771965...%3AMEBIDX%3AIT
http://www.ebay.co.uk/itm/2515753317...%3AMEBIDX%3AIT
Just means you can splice into the harness wires instead of the cars wiring to keep everything original and undamaged should you decide to remove etc.
The one in the link you mentioned doesn't ship to the UK so I'm going for one of the two I've linked instead, hopefully the fit will be good as i have had ISO connectors in the past which haven't fitted brilliantly so fingers crossed.