If someone had been killed, and assuming a witness/CCTV or dashcam was able to identify the vehicle, it wouldn't get out of the country.
If there were no evidence that identified the vehicle then like as not the driver would probably never be caught, the same as any other crime where there is no evidence to identify the suspect. In that regard his status as a foreign driver is irrelevant.
In the case of the person in the near miss the police have done nothing wrong, and their response is pragmatic as regards the realities of the law and practicalities prosecuting someone from overseas.
For death by and drink drive offences there are powers of arrest and, more importantly, powers for remand to ensure the suspect remains available for court. For lesser offences (not to denigrate the impact on the victim, that is simply how the justice system regards it) that is not possible, so even if he could be stopped a mile up the road he would have to be summonsed to court at a future date and the odds of him appearing are exactly zero. They never do. I wouldn't in their shoes.
Tracing the vehicle once overseas is difficult and resource intensive at best, impossible at worst, and as such can only be justified for serious crimes. And even if they did somehow trace him and Summons him he ain't going to appear, and there's nothing can be done.
It's the system. It sucks. Direct your ire at your elected representatives and not at the poor schmoes who are saddled with working it.
But these are what we call 20p questions. What it this, what if that? It's hypothetical. We know what happened, and I've explained the reasons behind thar.
