Is there any information out there on how to use a police training lead? We have just purchased one but dont want to start off the wrong way.

I can't give you any information I'm afraid - only lots of questions.  Please don't take offence I'm only asking to, maybe, help you answer your own question.
Why have you got a police training lead if you don't know what it's for?
Is it a 6ft or [don't know how long] tracking lead?
What do you want to achieve with your dog?

I use Mikki training/7in1 leads.  Great for walking loose, close, at heal, training inc.wait/stay/over/through -as in jumps, tunnels etc, initial tracking, securing dogs outside shops... they're about the same length as police leads, I think.
you could also try searching for police dog training - but a lot of that is control and restraint [of criminals] and could/would be dangerous to practice with a non-uniformed dog.

>> I use Mikki training/7in1 leads.  Great for walking loose, close, at heal, training inc.wait/stay/over/through -as in jumps, tunnels etc, initial tracking, securing dogs outside shops... they're about the same length as police leads, I think

I believe they are the same everything as 'police leads' but different material.  I used to use the 'police lead' on my rott boy but it hurt my hands so swapped to one of the same style but softer material - as recommended here on CD

I use training leads as normal walking leads I like them because they are strong and you have control .

when I am out on walks where I want my dogs to have a bit of freedom but dont want to let them free run I extend the leads.

When I am training a young pup  or older dog I use the lead to teach healwork ,puppy recall , or if doing agility you can extend the lead until you  feel confident enough to let your dog work off the lead.

roni

I bought a police training lead and collar from the first class we went to (police trainer !) really couldn't get on with it far to hard even after treating it. Would say it is about 6ft long with a ring on it to shorten, didn't get told there was any special way to use it any different from any other just the fact that it was good and strong with the option to shorten or lenghthen as starryeyes says at least you know it is unlikely to break if the dog lunges suddenly. Didn't get on with the collar as my boy is a longcoat and it was damaging his fur. Trainer had no sympathy for that , his view was whats a bit of damaged fur if you can control your dog better  my view was there is a compromise and there was.  
I have tried police trainers twice and found them too "this is the only way" and a little harsh for my likeing I couldn't manage all the shouting of commands and no treats 

Hi Furriefriends,
I have a long coated breed and did for years find it difficult to find a collar that didnt damage the coat eventually came up with this one http://www.earthdog.com/hemp-products/decorative-hemp-line/martingale-decorative-collar .

Oh thanks Starry they look good