Dont use the men that pretend to be taxi drivers welcoming you at the airport - they use private vehicles and will charge you an arm and a leg - please only use the official metered taxis!
London is one of the most vibrant destinations in the world. For something a little difference, you can venture out to Primrose Hill and experience a real London village feel with some of the best views over the Capital - the park and the famous hill offer some views not to be missed. You can also have lunch at Trojka, a local 'Russian' cafe which makes very good Blinis :)
I heard there is a lot of violence and kidnapping can happen quite frequently - is this justified or is the perception rather amplified by the Media?
Amazing city - do not forget the promenade des Anglais ;) the old antic market in the old town is great too. Loads of restaurants and bars to venture out to - definitely a fabulous place for a long weekend ;)
Absolutely LOVE Sydney - an amazing city, very diverse and cosmopolitan - Stayed there for about a week and got to see the Blue Mountains which isnt too far out away from the city and definitely one of the things to do - The fish market in Sydney is also not to be missed whilst the main harbour is a must do, being recognised as one of the best in the world
Paris is simply one of the most amazing cities in the world. I would really recommend you going to the Mouffetard market on the 5th arrondissement - every Saturday and Sunday. You will get a real flavour of what a French market is: from fruit to vegetables, chocolates to wine, cheese to fresh meat and fish..they have it all. It is sublime and not to be missed!