LPG installation check

I have no idea about LPG, Autogas, or whatever other names it may go by. My Hijet has a factory fitted option for LPG. I have no ida when it was last used, certainly not by the last owner. I think that a system check would be a good idea before I start filling it up, but whre on earth do I find an engineer? Whatever Google search I try, I get domestic LPG installers and service engineers.
As usual, any answer or any other advice will be gratefully received.
Thank you.

Great information, thank you.
I spoke to a local company and discovered that they stopped this work some years ago. They gave me a company close to 20 miles away. I mailed them and was told that they would visually check it over, then add a small amount of gas to the tank and pressure test the system. All being well, she will pass those safety tests and be ready to go. I have booked in for Thursday afternoon.

Don't be too scared. At least the gas evaporates when it leaks!!!  

Inspect the tank at the back, peel all the flaking paint off it, wire brush the rust off, see how rotten it is.

Plenty of Hijets have leaking petrol tanks but they don't have quite the same fear hysteria.

Put £5 worth of gas in it, have a good sniff about. Spray down all the fittings with soapy water watch for bubbles.

Flick the petrol/gas switch, see if it runs.