Looking at the number of pages on this subject , 7 or 8 I think, is is worth rebooting as to what you have or don't have, eg sparks and fuel and compression etc.
I have 2 C15s and each is different procedure to start

When you tickle the carb , does fuel actually dribble out of the carb visibly ?
It's not unknown for the floats and their needles to stick closed

New rods and old rockers , they have to bed in together.
Obviously , the pip is formed by the bedding in of the rocker ball into the cup , up to the point where the entire ball end is bearing on the entire cup surface.
Personally, I probably wouldn't bother , other that keeping a close eye on the valve clearances , which will be affected by this ball and cup wear.

Aren't these pips formed by the ball end of the rocker?
What are the rocker ball ends like ?

The c15 and B40 are definitely 2 different part numbers

This is the choke slide which is shown in the AMAL parts diagram.
It is used to aid starting.
It blocks or rather upsets the air flow when used.
Normally, you push the lever away to slacken the cable , thereby lowering this slide.
A PO may have changed levers causing you to reverse the action.

I've just checked my C15 bsa service sheets
Earlier forks have 1 seal , later forks have 2 seals
My 1965 ss80 has 2 seals
But I don't know the changeover date.
Remember oil seal lips downwards
You clearly have the later forks

From memory, there should be 2 seals per leg in the holder

can you actually describe the area of the leak if you cannot do pics?

Usually 1 is painted red to identify I think

I joined the bantam owners club when I needed guidance and help registering my bantams.
The dating officer Tim was very helpful indeed.
But also, as mentioned , I did have discussions with the dvla , who were very helpful , sending me forms and chatting etc , all of which were needed in the process of creating an age related registration number.
You might have someone visit you eventually to verify the bike's frame numbers and engine numbers.
The bike must be complete and roadworthy as part of the process , not a pile of dismantled parts.

And of course the bantam owners club.
Lots of help and guidance.
You can always ring dvla and go through the various options and speak to someone , I've always found them very helpful

When you say loud , is it exhaust loud or mechanically rattly loud ?

That's all I did , found a decent led riding pilot light for visibility.
This by the way   did not suffer the same as the hlight bulb.

I tried to use an led Lucas/wassell bpf headlight , but to no avail.
Supposedly it covered 6,12,24 volts.

Worked fine without the engine running but immediately on starting and running the engine , started to flicker and switch on and off.
Only to stabilise again when I stopped the engine.

I had a long and sensible chat with a technical guy at Wassell and jointly explored voltages etc , but it wouldn't have it, so returned the bulb.

To give you a background, all earth's and connections were soldered and 100%. I even tried changing the reg/rec as it looked as though spurious AC was bleeding into the bike upsetting the leds.

I finished up sourcing the lowest wattage bpf bulb and sticking there.