Lugs could be
Nervex Serie Legere Model 48/161
fork crown is different. I have a 1952 frame with these lugs, also with a different fork crown. It was not unusual.
Unsure why Carlton has been mentioned. The frame number is not in
the form listed on this site
And can you confirm that the frame number is different to the fork number by 3000. I have some recollection of that being a trait of one frame builder.
With a frame number so large your chances of identifying it are strong.
I agree with asking Retrobikes, and you could also ask the
Classic Rendezvous group but please carefully follow the rules. It is Dale's garage, and he has clearly stated rules.
Is there any paint under the purple?
or is there the smallest metallic fleck to it?