When I see those outrageously large wrapover stays, I think "Holdsworth", not "Carlton". I think the holdsworth wrapovers were often 1cm longer, at their widest point, than most other makes of bikes with wrapover stays.
http://www.classicrendezvous.com/
The serial number could be a carlton, and if it were, it would be a 1968. I don't know the Holdsworth serial numbering scheme. For many years in the 60's, however, both Holdsworth and Carlton made models that were nearly identical, i.e. exactly those Davis forks, prugnat pro lugs, etc.
I have a 1968 Raleigh Competition with long campy dropouts and bottom bracket routing, but that's the only instance I've ever seen of a Carlton bike with long campy dropouts and bottom bracket routing, and my bike has a full nervex lug/bb set.
- Don Gillies
San Diego, CA, USA