A little update. I wrote to Jerry from: http://www.carltoncycles.me.uk/carlton-links.htm
such a nice guy. Wrote back within 30mins of my message. This is his reply.......
Tricky. It looks every inch a Carlton Flyer from around 1960. However, the frame number is odd and there does not appear to be two small holes for a headstock badge that would have been there on a Carlton.
Carlton made frames for at least 16 other makes, some of whom were very reluctant to let it be known that Carlton made their frames (Anquetil?). However, this tended to be later in the 60’s.
One possibility that would date from that era is a Donovan. The Donovan family owned Carlton in the 1950’s and some quality frames were made with a Donovan logo in the form of a transfer rather than a headstock badge. Have a look at http://www.carltoncycles.me.uk/details/wanderlust.htm
. The frames were numbered differently and there are no records of numbers.
Worth taking a look inside the seat tube from the bottom bracket, sometimes you find works dockets tucked in there giving details of finish and model.
Another possibility – is there a different number stamped on the steering stem? Some 531 racing frames were numbered there.
Final possibility – Original Carlton refurbished by someone who rebadged and renumbered it.
The attached catalogue sheet gives the sort of specs that Carlton were offering for 1960.
Sorry can’t help further.