Shark fin aerial query, re-visited.

I tried getting to the bottom of this a while back, but it ran flat when I found out how expensive current aerials can be. I've found cheaper OEM examples now so wanted some help.

Here's my aerial (ugly, I know):

Here's what the connections look like:

Here's my head unit:

Here is the type of aerial I have found that I want to adapt:

I know the blue colour code relates to GPS (what I need).

How do I go about doing this? Can I go about doing this? It's essential that the GPS antenna works so the that I can use my sat nav.

I've found an aerial for a decent price, but it's still the best part of £50, so I don't want to drop cash on it to find it's a pointless exercise.

Help much appreciated.