Before I give my opinion I'll qualify it slightly... I have spent a couple of years of my life clearing up the results of accidents and seen some truly awful sights, as have the serving/retired police on here. That hasn't made me an angel and I would never pretend that I stick to every speed limit I see. But, 30 means 30, 40 means 40 and (generally) 50 means 50! I must confess that the white disk with a black stripe is, in my (wrong) opinion, fair game. I was lucky to get let off with a slapped wrist many years back when I was stopped doing over 100mph... It was the middle of the night and the motorway was virtually deserted. I got stopped 8 months later doing 43 in a 30 (dual carriageway and the limit had changed from 40 to 30 a few weeks earlier) which I accepted as my fault immediately... I learnt a lesson and slowed down!
The character you have described deserves to be banned for the maximum time possible... He got let off once before!