You can't sail from London to Cologne.
an hour and a half to two hours
3 hours about
4 days
i would say roughly 4 hours.
2 days
About 2 hours and if you take the M25 it may take about 4 to 5 hours
6 and half days
several days
Dover to London is only 70 miles and Dover hasn't got an airport. Take a train, it's much easier.
Depends on the boat and the crossing. Dover-Calais is about 75 minutes. Other crossings take up to 8 hours.
About 1.5 to 2 hours driving time.