They usually just have a compression fitting if it's a rigid pipe or a nut with o ring if a flexi. The valve on the tank will not let the gas out and it's an undo, remove bumper, fit bar and re-assemble.
Obviously you as mere human are not supposed to do it, a professional is supposed to. Based on experience of said professionals, if you are a competent home mechanic you should be fine! Wear gloves as you will get the gas in the length of pipe discharge and this is very cold when escaping!
If in doubt get it disconnected professionally though!

There are no rules or regulations regarding LPG systems on cars, any one can play with it, there are only misinformed garages and old wives tales.... Gas rules only apply to buildings....

Removing those four screws will not allow you to get it off...

There are two types of pipe that could have been used, one will have a nut and olive on a copper or plastic pipe, the other will be a rubber hose with a fitting on the end that just unscrews.

Whatever is on there will undo with a spanner, as said there will be a loss of gas and it can seem to go on a while as it will be liquid in the pipe, LPG is heavier than air so don't do it in a garage over a pit etc... Do it outside, crack the nut till it starts to come out, wait for it to stop hissing then undo it...

Refit is a reversal, don't use any thread lock etc on it, when refitted, go and put some gas in then spray the fitting with soapy water to check for leaks but I bet you don't have one, they tend to be pretty well made and seal well.... Pete

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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Many thanks for the info .i think I'm going to fit it myself ,and then get someone to do the electrics.
Cheers Tony

I think you will find the electrics are plug and play, supposed to be the easiest bit as long as it's the correct kit for the FF, not fitted one myself though.... Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-