You have 2 options, 1 buy a cross over adapter harness as pins 4 and 7 are switched on VAG's or 2 change pins 4 and 7 on the power harness, you can pick up an adapter harness for about £5 delivered off eBay, you will also need an iso to din Ariel adapter and you will need Mercedes style release keys to get out the stock Alana stereo, you can also use European release keys but they are harder to release the head with