Madrid Airport has many flights to London by Easyjet, British Airways and RyanAir
This would be London City Airport, which is located in the eastern suburbs of the city not far away from The Docklands (the new skyscraper district). However, this airport is restricted to mainly business and charter flights. So you're more likely to end up at Heathrow Airport, which is the second closest. Don't be too worried about distance though, as all airports are well connected to London. I'd rather take flights to Stansted Airport (which is quieter than Heathrow but much further away) than Heathrow (which is very busy).
London's he-throw airport
Barajas Airport is IN Madrid, so the question is a null point. (It would be like asking "How long does it take to get to JFK Airport from New York City?" -- The airport is in the city.) If the question means to ask how long it would take to get from Barajas to the downtown area, it would be between 25-45 minutes in a taxi (depending on traffic) or around 50 minutes by metro. The actual distance between Barajas Airport and downtown is 8.5 miles or 13.7 kilometers.
Heathrow is the closest to Central London London to Heathrow According the AA Route Planner (GB Edition) the distance is 14.5 miles, this will take about 0 hours and 40minutes to drive. London to Gatwick According the AA Route Planner (GB Edition) the distance is 28.6 miles, this will take about 1 hours and 1 minutes to drive.
Barajas in Madrid
The Closest Airport to Hasselt is Koeln-Bonn. But if you are in Cologne I think it's easier to take the train.
About 45 minutes.
0.18 hours
For a non stop flight by DC 10 it would take 14 hours. By one stopover at London plaese add 4 hours more. For 2 stopovers like Dubai (or Karachi), London (Shanon or Madrid) add again 3 to 4 hours.
About 1 hour 30 minutes, but it depends on traffic conditions at the time.
Half Hour.
usually about 9 hours.