Wouldn't worry about it.they've got to show evidence to prove that you were driving like a cock otherwise you can sue them to get all your expenses back etc.
Their just trying it on for the very reasons you said,to intimidate you to stop you driving,could be any number of reasons.
True what chip says about cops,you get good and bad but I feel the majority have lost their commonsense in this day and age and often just come across as totally unreasonable IMO.
Its not just a new phenomenon,I got pulled in my first car,fiat UNO 1.1 when I was 17 and to my horror,I found out the Mot ran out the day before!!
Devastated,I went and shoved a brand new ticket on it and went straight down the copshop to meet the biggest pig I've ever met in my life.he told me my insurance was invalid because it covered me on any car (????).then apparently because I hadn't supplied him with a logbook(not on producer) he was going to do me for failing to produce as well!!!of course,the Mot then reared it's ugly head and he started swearing at me then,"what the fucks this?now you've got 8 points on your licence" etc etc.
I was shitting myself for weeks,worried about losing my licence etc so I went back in to see a different copper who was so nice,really helpful.he told me I would be charged with no Mot as it was out when I was stopped but to tell the court that I'd taken it as soon as I found out and got it sorted,there were no points and only a small fine!!!
Cost me £20 fine £20 costs,about the same price as the Mot!!!!