We're looking for a pushchair to use in a capital city - think small pavements, crowds, underground trains.... 
We've started looking and have seen travel systems where you can use a carrycot clipped onto the chassis from birth, then change to the seat from about 6 months.
Our friends have a Bebecomfort travel system but they say that it's too heavy really and are changing to a Maclaren now their baby is 7 months old.
So, what we're looking for is light, practical, compact, easy to fold, with a carrycot attachment (preferably that can be used in a car) and that can be used from birth up until walking age...
If possible, we need the carrycot attachment to be light - we live on the 6th floor without a lift and although we'll leave the chassis on the ground floor, I'd like to take the carrycot upstairs with us.
Price isn't really an issue. My problem is that there is just so much choice on the market!
Another friend has recommended a Red Castle Citylink 2...
Any other suggestions?
Thanks!