2004 LPG needs a sevice

[emlclcy]

Hi all, first post
I picked up my 2004 swb van last night, the lpg was empty.
I 3/4 filled the tank and with a hot engine pressed the button on the dash with the slopping gas looking symbol, which made the fuel gauge on the rhs go to zero and a green light next to the gauge started to flash.
There is also a square button to the right of the ash tray which has a row of vertical leds I guess to show how much gas there is. When I pressed it I heard a solenoid click and the vans tickover stumbled.
I don't know if it has ever been serviced so I was wondering if anyone knows a decent LPG guy in Hampshire that can tune it up for me?
I don't want to run it and burn a valve!
cheers
carl