First Build - AES-1 AHAHAHAHA

[Scramblermatt]

Whilst I'd still be tempted to leave it a little longer before doing anything to the neck joint, you can obviously start to have a look and see if there's anything in particular stopping the neck fitting in fully. I'd rub some chalk on the pocket join area, push the neck in and the high spots should leave a mark on the sides of the heel. You can sand those down, repeat, sand repeat until it all fits nicely.

Not a great pre-wired harness you've got there. I'd be tempted to start again as the wiring lengths between the volume and tone pots are rather excessive and the wires will tend to flap about inside a bit. The pots with the green capacitors attached are the tone pots, the other two are the volume. The long bits of wire attached to the volume puts are the pot outputs which run off to the selector switch.

The red wire attached to the back of one of the tone pots is the ground wire for the bridge.

It's made slightly more confusing due to the factory wiring the pots in shielded cable, rather than the singles cores the wiring diagrams normally use. In some instances, you want to use the braid as a ground link, and sometimes it only needs to be connected to ground at one end.

So in terms of the neck, in the PGB instructions it tells you not to sand the floor of the neck pocket or the bottom of the heel as there is a break angle incorporated so I’m a bit stuck!

There is a gap on one side of the neck (shown before) and the whole fret board seems pretty high when the neck is in place...I measured it at 15mm from the body to the fret board.

Not sure what to do about this...I know you suggested the chalk technique but without sanding the bottom of the neck or neck pocket how am I meant to sort it out?

Does it sound right or is the neck not right?

[JimC]

... but without sanding the bottom of the neck or neck pocket how am I meant to sort it out?

I had to mess with the neck angle on my ESB-4 for a non standard bridge. Its not what I'd call super difficult, just need to be slow and painstaking, and I suggest not use sandpaper. I used new Stanley knife blades as scrapers, and a caliper and a little baby steel set square such as are sold for modellers.
Scraping the surface with the blade at 90 degrees to the wood gives you much more control and makes it way easier to keep the surfaces flat. With sandpaper, even with a block, I find it awfully easy to end up with a curved face. Perhaps the trickiest part is to establish whch are the correct surfaces to use as a datum. This involves much measuring with the calipher and much testing with the square. Make sure you check all surfaces are flat too.
With the scraping I usually scribble soft pencil where i want to scrape and check again when removed.
Long job, do it in a comfy chair with dust sheet, but I find the scraping much more relaxing and satisfying than sanding.
Caveat. I have no training, there may be better ways to work, but it seems much safer to me because its slow and controlled, and because he frequent checking required to renew the scrape here scribble makes it hard to go too far as is easy to do with plane or power dander