Re F4 INAS performance, it really was not all that bad. Sometimes you got a real rogue set but it was easily identified as such.
When we went to the Falklands on the first F4 deployment from Ascension, we checked in early (well, for us as on AD normal practice) and I got a real shock when the INAS refused to align. With 12 Victors taxiing around to take us there and starting to panic as the lead crew (of 2), I eventually realised that the wing magnetic sensor was not sending the correct signals to the INAS for a coarse align. I found the checklist details for a wing folded align, which I had never done before and went through it. That seemed to do the trick (I hoped) and we set off for Stanley. Being an ex Canberra nav of old fashioned training, I decided not to integrate the various feeds I was getting re position info from the INAS, Victor updates and my trusty manual airplot. However, I did note that they all seemed to agree vaguely. Anyway, I turned on the Radar at an estimated 180 miles to go and there was the Falklands painting beautifully after 6000nm. When we landed, no updates to the INAS remember, and after a very dodgy align sequence, the INAS was about 20nm out. This after 8.5 hours flying through some severe turbulence and easily enough performance to find an area the size of Wales.
No, the F4 INAS was pretty good for its day.