My understanding is two oficers are necessary North of the border in Scotland.
As you haven't been given an actual speed, I would have said you haven't actually committed an offence in the eyes of the law. Usually any NIP documentation cites the exact offence you have committed (i.e. 46mph in a 30mph limit etc, etc).
My advice would be wait for 'RUSHJOB' (member of this board/club) to come along and give his expert opinion on this, don't sign (or return) anything on the paperwork until you have sought expert advice and visit
www.pepipoo.com.
Sounds a strange one....
Guido