There is no such thing as "trying to intimidate".
You either felt intimidated or
you didn't because intimidation is subjective, you cant deflect/externalise/project an internal emotional response.
I've been in situations involving hardened gangsters, so to me and most other men, finding a measly "chav" intimidating just from their gaze is comedy gold
Did these guys actually take interest in anyone's business except theirs? Did they even say anything to you?
What's worrying is that you pre-emptively call the police for no other reason than they were "trying to intimidate". Why not just leave their business to them and let someone who actually got affected by them call the police, if anyone did?
Also the belief that you have done a good deed. You might want to realise people from the neighbourhood who loiter around are actually the first people who would rush to help if they witnessed something ACTUALLY bad going on in their neighbourhood.
Who's to say you didn't cause the removal of vital witnesses for some ACTUAL crime which took place 2 minutes after the officers had to shift them on??
Who's to say those three guys smoking their joint didn't deter someone else from an opportunistic crime minutes earlier?
What if the diversion of those officers allowed some opportunistic crime to take place somewhere where the officers would have been randomly passing if you hadn't intervened?
Just remember that the world doesn't revolve around you and certainly not around what you assume is intimidating.