Thanks for the input, I got a rather insistant with the Dulux emusion on the BB and out popped "E 5816" as a frame number, which is matched on the fork stem.
What I've found on the web =
January 1950 – October 1956, first two numbers = year, next = month.
November 1956 – July 1958, in receiver so a black hole !?
January 1959 – Mid 1967, Holdsworth ownership, sequential until about 31000
So it's not a Claude unless they made frames when in receivership, in which case it'd be a Jan 1958, #6.
Starting 1947, a letter indicates the month A-L. Then a four or five digit number, the first digit indicates the year. Thus number A7151, was built in January 1947.
In 1950's the system simply used the prefix 0, 1, 2 or 3.
But they stopped making frames in 1953 - so a 5 as the year would not fit !?
Also I understand they used to stamp the number on the dropout.
So it may not be one of them :-(