Seems to be the dash-cam car needs to slow down. The car turning in may have been came upon an obstruction and thus forced to slow down or stop (such as an idiot walking in the road). But they speed the dash-cam car was going, together with the blind spots, would also make it more difficult to judge their speed. Live and let live? Just one of those things..
Cash for crash convoy? Or just arrogant, violent people preying upon a lone pregnant woman? You did exactly the right thing: do not react to them, do not engage with them. Drive on and pull into somewhere populated such as a petrol station, shopping precinct or even police station and keep the hand on the horn. They will then most likely be on camera. If they follow you enter a premises and call the police ref drunk/dangerous drive making threats possibly in an attempt to steal or crash into your property (vehicle). Stay where there are people. The a******s will then have screwed themselves over by the time their tiny brains realise it. Cowards such as that described don't like being exposed!
My honest impression after seeing 1000's of comments and video's is that, the Highway Code needs updating. The Code has - in some people's mind - effectively become a license to kill. The devil is in the detail: some drivers interpret "should not" as "can", despite the level of danger involved. Why is this so? Because law is an ass and it doesn't want to cope with the workload of many, many bad drivers being brought to justice more severely than they would having been let off with a "talking to" or a "caution". Most people don't over-take through pinch points but some do, and they do it with impunity because the law lets them..
Location:
Alexandra Road South
Whalley Range
Manchester
M16 8NH