I am trying to download and install double doplers met police cars helicpters, ambuances etc,. I have managed toi successfully managed to install my ambluance and fire engine and the met police helicopter. Butnone of the police cars willl load up i cant get the siren to import into open iv comes up with error message,and i cant gethe paremadeic uniform and co19 uniform to load up.Any help or ideas will be much appreciated. Kind regards Adam.

Are you installing them in the right places, cars are all over the place in dlcpacks folder.

You will find police, police2, police3 and police4 in almost every dlc folder. I'm not sure why this is, but you have to find which specific dlc folder goes with the specific vehicle. Normally car mod read me files will tell you where to replace 

I usually go with the latest patchday.

yer i am as check the installl guide with them before hand to make sure.

it might be worth ding team viewer so u can see if u can help me as i dont use open iv much.