The frame number will be stamped into the steel tubing
You'll find it just below the seat pin (seat bolt, call it what you will) at the top of the seat tube
It 'may' be obscured by the decal with Paul Sherwen's signature on it!
The one you have photographed is 'another' serial type number, and to be honest I've never found anyone that knows what these are!
The frame number will start with a capital N, the remaining numbers will date the frame
Nice bike btw