My opinion: if he was a foreigner, slap the fine on him and tell him the motorway is not for cyclists, make sure he understands and have a laugh about it. If he was a normal fully functioning adult non-foreigner, slap the fine on him and give him a hard stare.
the sort of cyclist that, having ignored a red light outside the British Library on the Euston Road, knocked me flying off the pedestrian crossing and told me I was a F-ing menace.....
and the sort of cyclist (always dressed in all the gear) who followed me home and had a go at me outside my house because he said I'd cut him up. It actually scared me for several days. I hate cyclists on main roads.