None, if you cycle! If you drive, it depends on the fuel efficiency of your vehicle and your driving style.
It depends on the cost of said petrol and the efficiency of the vehicle in "miles per unit of petrol". You didn't supply enough information.
From Cardiff to Glasgow is some 400 miles and would cost about £75 in petrol.
At 15 miles per gallon, 7 gallons of petrol.
Depending on driving conditions - about 2.5 gallons.
It would cost (2.4) times (the cost of one gallon petrol). Also, add cost of tolls, food, etc.
500 miles is always 500 miles unless it's nautiical miles. I'm not sure if 500 miles in petrol would be classed as nautical miles.
300 dollars
274
£10 approx dependent on the price of a liter at the time
It depends on how fast you travel.
Depends on the fuel mileage that the vehicle you are driving gets and the price of fuel along the way.
18,800 divided by 35 = 537.14 gallons of fuel required to travel this distance. 537.14 x 6 pounds = 3,222.84 pounds.