Empty Pockets,
I see that your query hasn't had any answers. It's been some time since I worked proposals on aircraft for Flight Inspection (the overall maintenance of and verification of Navaids) but here are a few pointers. ILS checking is one of the most complex aspects of Flight Inspection. Companies that provide airborne equipment to do this include Sierra Systems of the US & Litton Systems of Missasauga, Canada. Two manufacturers of ILS are Rhode & Schwarz (Germany) and Harris (US).
Hope this helps.