Non issue, random self oppointed police man interfering with local truck driver going about is normal day of work. The Op states he wound his window down first and started the gestures!!
What does 3 fingers mean in the Highway Code and how would the trucker know what you meant by showing 3 fingers out of a car window?
Not condoning speeding in the slightest, but how do you know he was going 60 when all trucks in UK are restricted to 56mph, yes it’s possible to get a fully loaded truck up to 60 but you need a very long downhill on a motorway.
Very much doubt any truck would be on the limiter going through a 30.
Non issue made into a confrontation by Op. it’s not your job to police the roads, better leaving it up to those who get paid and know what their doing.