Captain 87.
The airbus is an aircraft like any other, if it all goes wrong then you revert to basics. You would get attitude info on the isis along with airspeed and altitude. You also get glide and loc info. As well as that you have the standby nav instruments for VOR/DME/ADF info, so all in all you are just reverting to a jet powered seneca.
My point in my previous post, which having reread didnt come across, was that at the point when it all goes dark and you are relying on stby instruments maybe an ILS would be the most desired choice.....