Mal Drop,
when I did the HEART job the HINS fit was way behind schedule. We interviewed the chap 'running' the program and he was not bothered at all.
It appeared that MOD had given the GPS/INS bits to different firms and no one was accountable for the subsequent delay. Each blamed the other !
I remember the big yellow 'brick' that masqueraded as a GPS . I think they were designed for tanks.
It is oft forgotten that it was not really until GW1 that MOD woke up to the fact that for the SF crews to operate effectively they badly needed some decent kit.
This of course harks back to how the SF Flight was set up in the first place.