Back in the 60's they had a professional CX rider, Eric Stone, who was very good and rode for several brands before retiring. I think Eric was a runner before he tried CX and made a big mistake (possibly due to naivety and not understanding the petty officialdom of cycling in that era) in wearing a trade top in an event. For this he was duly declared 'A Professional' and, as the top may (or may not!) have had 'Dawes' emblazoned on it, he rode for them for a while before being snapped up by one of the 'main' teams. Whether his CX frames were actually Dawes made is, as usual in these circumstances, open for debate.
However, as for them actually selling their own CX frames for the general market I would say is doubtful as the sport wasn't really 'big' enough in those days to warrant the expense.