Just bought 4 Kumho Ecsta KU31 tyres from Black Circles and had them fitted at my local branch of ATS.
When I went to collect the car the fitter advised that whilst all tyres were labelled by Kumho as 205x50x16 he had spotted that one was actually a 205x45x16. Apparently he has had this problem before, mainly with Avon tyres, as a result he now always checks the markings on the sidewall when fitting any tyres.
I will now always check new tyres for correct size, irrespective as to what it is labelled, as not all fitters may be as diligent.
Full marks to ATS in Doncaster and many thanks to Black Circle for getting a replacement out next day.