My disco is sitting on the bump stops on one side the drivers side only. Does this mean the bags or compressor is away.

Hi, mine was doing the same a few weeks ago, every morning the passenger side was right on the stop and the drivers side was nearly down.
Start your disco wait for suspension to levels itself and spray soapy water on the air suspension bag, I found a load of tiny bubbles coming out from were the bag curls under at the bottom.
Replace with new Britpart bag 2 weeks ago and stayed up ever since, make sure you buy 2 new C clips for the top of the bag.

spot on, its the air bag on that side needs replacing, about £80 a go, but both sides should be replaced at the same time. easy job, or about £50 for garage to do it, theres loads of threads on heer on how to do it though