Chezzy, to save any future argument about what does or does not constitute an ELCB and how they differ from circuit-breakers, I refer you to the Naval Electrical Engineering Training Manuals at http://electriciantraining.tpub.com/index.htm and suggest that you go to MODULE 03 - INTRODUCTION TO CIRCUIT PROTECTION, CONTROL, AND MEASUREMENT then have a read of Chapter 2 Circuit Protection Devices which will give you all the information you need to verify that what I've said above is completely correct.
In a household meter box, the fuses are simply links in the active conductor only, and while ceramic fuses can indeed be replaced with plug-in circuit-breakers of the type which Bunnings and other places sell for around $10 each, a circuit-breaker won't trip until the current load exceeds its rating, which may be 10A or 15A. Therefore, they do NOT offer any additional protection whatsoever to somebody who's unfortunate enough to come into contact with the active circuit, and electrocution will almost certainly result.
ELCBs and RCDs, on the other hand, need to be hardwired into both the active and the neutral circuits as they continually monitor and look for any imbalance between the two, and if so, they will immediately trip. The ELCB will typically trip if it detects an imbalance of as little as 30mA (i.e. 30 one-thousandths of an Amp) which is way too little current to stop a human heart from beating.
To reiterate, it is not even possible to manufacture an ELCB which plugs into the active circuit only because it needs to monitor BOTH the active and the neutral simultaneously, something it can't possibly do if plugged into a ceramic fuse-holder which protects only the active circuit. QED.
