I particularly like that technique of saving the price of a neutral bar by ramming multiple neutral wires directly into the bottom of the earth leakage breaker.

I'm not sure why you'd require 4x lighting circuits unless the house is enormous. If you're planning on putting everything on earth leakage then be sure to IR test all the circuits first, it can save a lot of misery.

TBH I'd strongly suggest you get a good electrician to help you out. Some of those circuits don't have a CPC (earth wire), they are using the steel conduit as the earth. Those circuits particularly need testing and visually inspecting to ensure they're safe and if any changes are done to the installation you really should rewired with an earth. Also the earth bar doesn't appear to have a main earth wire from the supply so it's highly likely the main earth is via the steel conduit of the incoming supply and via the steel chassis of the DB. Again this arrangement needs testing and inspecting before proceeding with any other work.

Please get a competent sparky involved, it only takes some corrosion in the wrong conduit to cause a grave safety hazard.