My estimate is for a petrol Ford engine in the era just prior to the required crank angle calibration type engine. Parts and labor being a variable I think around $550 usd is close.
In pounds sterling that’s roughly 430 or 460? Best guess from an American without an exchange rate chart. Avoid non Ford belts and tensioner! If the parts man advises you to get the tensioner bolt as well, heed the advice and get it! Good luck!