OK thanks Tim.
I've downloaded the openaip UK airspaces file but it's in a .aip format - from what I can gather from the XP11 forums, it needs to be in a .txt file and added to a new 'Airspaces' folder in Custom scenery.
Would it simply be a matter of opening the .aip file in Notepad and saving it as .txt and then adding it to CustomScenery/Airspaces?

I'm coming back to Plan G after a while, updated to v4.0.0.258.

I can see from the v3 manual that Airspace boundaries will not show when the sim is XPlane (11.55).
Forum posts relating to this issue are quite dated now - I wonder if it is still the case that boundaries won't show up if the database is XP11?

If so is there a work round? (apart from buying another sim and merging the data) - it's quite limiting not to have airspace boundaries when VFR-ing around the south coast!

Also does Plan G integrate with Navigraph data in any way? I can't see a reference to it.