They did build over 450 of them which served in 20 different navies and 5 Police and Coast Guards. The usual routing for props like this would to be find one in the knackers yard or but it really cheap and do it up cosmetically then blow it up. A perfect example would be HMS Amethyst which was dragged out of the breakers yard to portray herself in The Yangtse Incident (or Battle Hell, as it was known in America. ????) By the time the film maker got to her the engines had been removed so HMS Magpie stood in for her when required to move.