Hi Henry, Nice bit of progress! I think you had the needle valve upside down in the float chamber which is why you got overflow. The solid conical end goes up into the valve seat and the spring loaded pin end contacts the float assembly. You may have figured this out already(?)
It's also work checking the float heights while you have the float chamber off. If they aren't correct you will never get the carbs to balance.
Just one other word of warning is that heat shield under the carbs is highly likely to contain Asbestos so handle it careful or better still replace it with a modern alternative. Double bag the old one and take it to your local disposal centre.
Looking forward to seeing it running👍

I have learnt so much from watching you because you are learning as you are going and often make mistakes, this opposed to someone who completely knows what they are doing so thank-you.
I truly admire your hands on give it a go approach, thank-you once again for giving me a certain level of confidence to try more mechanics however basic they maybe.

He tapered section of the needle faces inward towards the needle

needle valve upside down sharp end closes off the flow

Needle valves in upside down. Won’t seal that way round !

If I'm not mistaken fuel filter is on backwards...?

Hi Henry.  I was wondering how long it takes for your fuel to come up to pressure?  My pump now takes a good 20 or 30 seconds  to reach pressure and then continues to tick every couple of seconds... can't find a leak anywhere but didn't do this previously.