In other words have the days of Stop Watches and Charts long gone in modern Fast Jet fleets?
For all practical purposes, yes. In the 80s and 90s (and in some circles into the 2000s) map and stopwatch lived on as the back-up to inertial navigation. Nowadays inertial navigation is itself the back-up system to GPS or terrain profile matching, and we don't need to waste much time on the back-up to a back-up! All of the MDR associated with map and stopwatch is still used to cross-check the numbers churned out by the computers (for time, drift, fuel etc) but actual map-work itself? Not so much.
Losing a HUD and HMS would not have any significant effect on the safe operation and navigation of the aircraft - as stated by others, flight safety-critical functions are backed up elsewhere. However it could entirely remove the ability to aim guns or visual air-to-air missile shots and would probably force the pilot to spend an unhealthy amount of time looking at heads-down displays for tactical information. It is this effect on mission capability, rather than any effect on the basic aspects of flying, that would be most likely to handicap an aircraft suffering display failures.