It it is uninsured then it is probably not taxed either and if it hasn't been declared SORN, an be towed away. Even if it has been declared SORN, it can't be parked on a public highway, must be private land.
Yes they have every right to remove it, if it it on public property, and it is the car that is insured thats why if your car gets damaged sitting in the kerb while you are indoors you can make a claim and get it repaired, if it was just you that was insured you would not be able to do that.