Miss:
Culture
Multiculturalism
Feeling part of the world rather than in a bubble
Question Time - the programme (not Q&A here)
Depth of conversation
Open mindedness (racism is more evident here on a day to day basis IMO)
Decent music
Being assessed for my skills when applying for a job rather than being British then assessed.
Not being so ripped off with the price of everything (there appears to be a massive disparity in the same product being sold in one place compared to another)
Sense of humour (OZ's get the joke, the just don't find it funny, generalising I know)
Laughing at oneself - self deprecation
Dont Miss:
The stress of London
Attitude of some people
Pointless violence and opportunistic violence (muggings etc)
The general dowdiness of London (not central)
Parking inspectors (much more easy going over in Sydney)
Weather in general