It would be unreasonable to expect a buyer to go round with a measuring tape and check every minuscule detail, surely? The diameter of the circle of stud holes is 6mm larger than required. I don't know about you, but I can't discern a 6mm difference purely by sight of 2 items within a couple of feet of each other.
I relied on the size described being incorrect. The seller has already conceded that it was his mistake for not checking measurements properly.
Quite so. If the size of the stud holes were a foot out, for example, it could be difficult to say it was truly a sale by description. 6mm is a different story. I think you would not have too much difficult persuading a court of your reliance (not that it should ever come to that).
There is no general requirement for customers to verify descriptions, as you say, with a tape measure or whatever else. You cannot very well measure something in OcUK's warehouse, for example, can you? Neither can you test an 'oven-proof' dish in Tesco to see if it is really oven-proof. You rely on the description being accurate.
The key point of s.13 (
http://www.legislation.gov.uk/ukpga/1979/54/section/13) is that the sale is
by description - s.13(1). It can still be so despite the goods being 'exposed for sale' and your selection of them - s.13(3).
As I said above, it depends on whether you relied on the description, which would it make it a 'sale
by description'.
Obviously, do not place too much reliance on my or anyone else's advice either, since we are not in full possession of the facts (there are always further considerations, for example, whether you accepted the goods under s.35 - you need to tell the buyer you reject them before you do something inconsistent with his owning them, which it sounds like you have done), but hopefully making this iniquitous seller aware of your legal rights should spur him into action.