To add my 2d penny worth, Entwood is exactly right.
A police patrol, who I was with at Folkestone last year, had need to remind the owner of a real American police car, that was in a company car park next to the police station, that he must cover up all its blue/red police lights, cover the police signs, and never use the two's on the highway. Although the view was taken it was unlikely that the English public would be fooled by an American police car in Folkestone, the law still had to be maintained and enforced.
There was a case as well last year of a car, just like the OP's, that was used to fool motorists into pulling over and parting with cash. They were caught. The OP takes the risk of being tarred with this brush and being accused of far more than impersonating a police officer!
Finally, remember, there is far more to being a police officer than running around with the blue's and two's on. It is only the childish who think they can be 'just like the police'. Just imagine the constant responsibility involved, and if you were mistaken for real police at an incident you would certainly 'feel' that responsibility for a short while, until the real police arrested you!!
