I actually converted to helicopters when I was working in Sydney for a year. For those who've not done it, if you imagine a trip from Bankstown airport, in the west of Sydney, north to the Paramatta river ( which is the official name for the river which ends up in Sydney Harbour ), then you fly at 500' from Ryde bridges, eastbound to the southern pylon of the Harbour Bridge, then climb to 1000' over the outer part of the harbour. That's to keep underneath the departures and arrivals from Sydney International ( Kingsford Smith ).
You speak to Bankstown on the way out, then change to the R405 assigned frequency and make blind calls to let other users know what's going on. You keep right ( as standard ) of the centreline of the river, clear of the houses on the land, and it's a really impressive trip. It's helicopters only between the bridges at 500'.
To exit the Sydney area northbound, and to enter southbound, there are also lanes of entry and exit, defined by lights on buildings which are visible from the air, with defined heights and frequencies. You only talk to a controller when in range of Bankstown.
There are also defined helicopter entry routes to Sydney international, dependent on the runway in use, but I never went that way.
Now the harbour trip is great fun, and it also works because people stick to it. I suspect the reason it isn't set up like that in the UK is that there's a tad more paranoia about the consequences.