Birmingham international airport is 122 miles from Cardiff
London Heathrow Airport, is 137 miles from Cardiff.
Birmingham is closest by 15 miles
Heathrow is slightly closer but there are good transport links to/from both of them.
Gatwick Airport is closer to Dover than Heathrow Airport. Gatwick is approximately 90 miles away from Dover, while Heathrow is about 110 miles away.
London Heathrow
yes, much bigger. heathrow has 5 terminals spread across 1227 hectares (12270000 m²) and Glasgow has 2 terminals and about 4-5 times smaller than heathrow. also heathrow is used as hubs for many airlines.
The distance from both is much the same so it depends on which one is most convenient for you.
The closest main airport to Oxford is Heathrow. Luton, Gatwick and Stansted are all much further and roughly the same distance from Oxford.
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.
The nearest Hilton hotel closest to Heathrow airport depends on which terminal you are flying from as there are two Hilton hotels in the same vicinity. However one is closer to Terminal 4 and the other is close to Terminal 5 which is a distance away from Terminal 1-4.
Birmingham
Stansted Airport (northeast of London) is smaller, budget-airline focused (e.g., Ryanair), and farther from central London (~40 miles vs. Heathrow’s ~15 miles). Heathrow is a global hub with more long-haul flights, better transport links (Heathrow Express, Tube), and amenities. Stansted suits cheaper, short-haul trips; Heathrow offers broader connectivity and convenience.
Luton is a town about 30 miles north of London. It is also home to London Luton Airport. Heathrow is a larger and closer airport but frequently domestic travel and sometimes international travel is cheaper when done through Luton.
From London to Wales is 135.78 miles / 218.51 km. Could not find anything closer than that :-) From London to Wales is 135.78 miles / 218.51 km. Could not find anything closer than that :-)