The measuring line on the Audi is 7.8 cm, the spacing line is 5.8 cm. 1733 x (5.8/7.8) gives around 1300 mm. Which is 4.3 ft
Here's the link to the Highway Code, 159-203
"give motorcyclists, cyclists and horse riders at least as much room as you would when overtaking a car (seeRules 211 to 213 and 214 to 215)."
Which to my mind is as clear as mud, since I don't believe there are any explicit guidelines for how much distance you should give to overtake a motorised vehicle.