Fuel filler cap 1

Decided to tackle the fuel filler cap today, I'm going with the Aston type. First of all I checked the center mark for the fuel neck to be installed. Happy with that I took out a 76mm hole saw and drilled the hole for the neck. I've been lucky so far that everytime I need a hole saw on the project I had the right size,
Next I added a couple of the gaskets supplied with the neck and cap and screwed them together, this meant I could set the cap in the right position on the car. I put a small bit of masking tape on the body and a bit on the filler and marked the 2 when the cap was in the right position.
Once removed 6 holes need drilled in the filler neck flange, these are pre marked underneath so easy enough to do with a 4.5mm drill bit. Once that was done on the top side I recessed the holes so the M4 button heads would sit flush.
Next the filler neck went back on the car lining up the masking tape marks, the 6 holes where then marked and drilled out on the body.
Simple as that ready to go on.
Well almosttttttt I had read somewhere that a breather needed fitted to the neck though there is already one in the cap. Flicking through the GD CD I seen the breather setup and also reading Simon's blog I knew one needed fitted. Firstly I didn't have a 1/8 npt male to female fitting and I didn't have a npt tap. Hmmmmm how to get round this