Personally I think it can vary from location to location. I have a great deal of sympathy with the assertion that the roads in South & South East Essex, for example, are worse than other areas of the country (as BTFB often refers) mainly because of the type of driver that resides there. Commuter belt country does not appear to generate safe and responsible drivers IMO. Commuters straight off the trains from London are a nightmare - after making a killing on the trading floor they just continue in the same frame of mind going home. If I didn't know better, I would say the closer you get to the Ford works of Dagenham and Dunton the worse driving tends to be. By contrast, riding in the City of London and other areas of Essex (North and East) I rarely get problems with other road users except cyclists and motorcyclists in the City; the latter of which will become more of a problem as bus lanes open up.
In reality it is the 5% of poor driving which gives other motorised road users a bad name regardless of location, but the 5% found in Essex are complete shoots. Bad and poor driving, often intentionally bad, and up for a fight as well if challenged.