In an ideal world the ILS should be within the controlled airspace but like quite a few in the UK, it sadly was not.
There are lots of posts saying something along these lines, and others saying that extending CAS around all the airports with instrument approach would eat up large quantities of class G airspace.
Where there is an ILS in class G it is marked on the chart. If I am flying near one I am certain not to cross it at a height which would put me on the glide path. Would it not be possible to give an implicit extension to the ATZ along the ILS glide path to make avoiding this area required rather than just sensible? It would only need to be 500ft above/below the 3 degree glide path, and a short distance to either side, and would take little airspace. I guess most pilots avoid this piece of airspace anyway.
I'm not suggesting this would have been helpful in this sad accident, just responding to the issue raised above.