Don’t worry on this front, all the measurements are standardized across the industry and unlike mattresses there is no difference between beds/headboards bought on the continent and those bought here.
Here is a guide should you wish to make 100% sure:
– 3ft Single headboard = distance between holes = 24″ = 61cm 4ft
– Small Double headboard = distance between holes = 36″ = 91.5cm 4ft 6
– Double headboard = distance between holes = 42″ = 106.7cm 5ft
– King Size headboard = distance between holes = 48″ = 121.9cm 6ft
– Super King Size headboard = distance between holes = 60″ = 152.4cm