N7Spartan

Typically you'll find selfish pilots don't do what everyone else is doing - for example requesting a runway that is not the active runway, not accepting visual separation with other traffic, not cancelling Instrument Flight Rules (therefore making separation standards ridiculous when everyone else is operating visually), performing an instrument approach with aircraft in the visual pattern.

It gets even more complex when people are flying different aircraft types and performance standards in the same area, and the normal safety buffers are eroded when people start doing things abnormally.

These are just some examples but given the complexity of air law and procedures, there would be countless more that I am missing.

Take a look at the ICAO Phraseology guide under the Approach section. I am not sure what the manual of standards specific to the UK says but the idea is to provide distinct clearance to commence the vertical profile of the IAP. In my experience the US way (cleared for the approach) is not always seen across the world.

The vast majority of airports in Australia do not have 24 hour ATC. If you end up as a terminal controller chances are your tower/approach service is not 24 hours. The centre airspace is 24/7/365 however.