Dear VAS
You can check out "Richard's Stansted Airport website", produced by an enthusiast but with a lot of worthwhile information. It has links to the airport arrival board (so you can get a feel for what punctuality is like here), photos of the airport, and links to all the ground transport options we have been discussing. It's on
www.fly.to/LondonStansted/
If you did decide to come back from Italy to the UK a day early there is no need to toss the tickets already bought; the Ryanair website explains the flight change procedure, although you can't actually do it over the web and you have to call the phone number they quote. Do it now because their fares can rise in the few days before travel and you get charged the fare applying at the time you rebook it.
I have found Air NZ long haul to be similar to British Airways, and that is a compliment to two good airlines.