They were and are still in the codes somewhere! They haven't been used, other than as a main-fuse protecting the entire consumer unit, since the early-mid 80s.
In general, where a new circuit is added to a neozed/diazed board the electrician will add a breaker. The boards use the same DIN rail system.
In many cases the fuses would have all been replaced.
Diazed fuses are no-longer permitted in new installations. This has nothing to do with the effectiveness of the fuses but rather more to do with a potential shock hazard when changing them. Modern Neozed and Minized fuse holders don't have this problem.
Neozed is permitted, but MCBs are recomended and have been the norm for quite some time.
Most installations from the mid-1970s onwards are MCB based and the standard siemens and hager MCB boards begin to appear around that time. However, Fuses, were still being installed by some electricians right up until the mid-80s.
Neozed fuses are STILL the norm as the main protective device on almost every consumer unit in Ireland and it's only in the last few years that we're seeing 63A / 80A main breakers appear.
Normal set up:
63/80/100A supply fuse (typically BS or IEC) sealed.
Meter (sealed)
Main isolating switch (power company provided [built into some recent meters]) connections to this switch are sealed by the contractor. It's designed to safely and completely isolate the system when it's being worked on and not for switching loads.
Consumer Unit:
Main switch (for isolation)
Main fuse (commonly 63A neozed) Main MCB has started to replace this little by little.
to 30mA RCD (where required i.e. not necessarily on cooker / lighting circuits (in older installations) )
to final circuit MCB (or Fuses in old installations)
Where MCBs are used 20A radials normally feed the sockets. (16A MCBs are sometimes used)
Where fuses are used 16A radials normally feed the sockets.
32A ring circuits are also used, but not quite to the same extent as in the UK.
(BS1363 sockets and fused plugs are the norm in any modern installation here (they begin to appear in the late 50s/early 60s). ( Schuko remained a permissable option, but was not widely available and was rarely used.) Round-pin BS546 was also used but disappeard as soon as BS1363 became available. The 5A version is still used in lighting applications. The 15A version was common place in theatre lighting but has been replaced in recent years by blue CeeForm industrial plugs (required by the health and safety at work legislation) )
Fixed appliences are almost always connected by means of a fused spur in both ring and radial systems.
Lighting is normally 6 or 10A depending on how it's configured and what the loading is.
Cooking can be 32-45A (UK style socket/cooker switch cooker control units are not permitted as the socket would have no RCD protection)
Instantanious showers are the same but ususally use an RCBO or a seperate RCD/MCB combination.
