It's been awhile since I updated this thread as the hangar is as done as it needs to be but in reality it's not finished yet.
One of the pieces of GSE for this is a nitrogen servicing trolley from DJ Parkins' Flightpath range. It is mostly white metal and a little bit of etched brass, I have only done the chassis and regulator housing so far. When the glue has cured it will get a coat of green paint and be assembled. After that the gas bottles will be done in light grey and also added.