Hi guys

Not been around here for some time due to owning a fake swedish car for a few years, however, I'm back and I have a question because I'm a bit green with some stuff.

Right, So I bought my Golf last weekend. Upon viewing I found the OE stereo had been replaced with some touchscreen carplay thing, as, y'know, just run it off your phone, but the original was on the back seat. Anyway, I'm not phone dependant and I have a lot of CDs.
The other thing with the carplay unit was it came on as soon as I turned the key, which I don't like, and there didn't seem like an aerial was connected either, so the radio was not an option either.
So, I popped the surrounding facia off this evening, and unscrewed the unit from the car. Behind it was a mountain of wires, splitters, and harnesses connecting everything to everything else. I par it down to the bunch of wires that go in the the back of the plug with the pull down clip, and those 2 black wires with the right hand connectors on. I also notice the one red wire that I think is powering the car play unit is on a separate wire, disappearing behind the dash.

I plug the main one in to the old unit, and connect the other two connectors. Turn car on, stereo doesn't come on. So I go online, look for fuses.
Fuses, end of dash board. I pop cover off, lo and behold, red wire coming from carplay is plugged into F2, with a holder fitted with a 10 and a 15amp. I look and refit the correct one on its own. I try the stereo again, still nothing. I look down the list, "audio device" is F28 or something, it's blank, I go to put a fuse in it, it doesn't have terminals.

I now find there's an "audio device" fuse in the engine bay fusebox, F18, it too is empty. I put the correct fuse in the slot. I try the stereo again, still nothing.
I try a volts meter on the 2 pins on the connector that I think might be the power wires. Nothing.

Now I've run out of talent. Would you guys have any suggestions? I've tried to include as much info as possible here.

One thing I did notice. The rear connector house what appears to the two iso connectors, as was the standard, and one plug with micro pins in, blue I think, but the stereo unit has 2 positions for micropin connectors. Am I missing something?

Answers on a postcard please, failing that, commenting below may be more helpful.

Many thanks in advance.