P.H said:I wouldn't know about the three you have. The one I linked to is 25.8.
Here it is from anotheer supplier, giving the clamp size as 25.8;
http://www.shinybikes.com/product.php?productid=16743
And another;
http://www.ribblecycles.co.uk/productdetail.asp?productcatalogue=ITALHBSR750
Sorry, didn't spot the clamp diameter on your original link. Looks like they've caught up with modern standards.