No, there's no set limit - indeed, many sellers often offer a one year guarantee - but the small print then says "this does not affect your statutory rights".
The law says that the item should be fit for purpose for a reasonable time; and what's reasonable depends on what you are selling.
For example. One customer wore a pair of shoes twice; they fell apart, and the seller said they were a fashion item, not footwear as such. The seller lost.
If you sold a dining table that collapsed after a year, you'd probably still have to refund. But if the shoes fell apart after a year, I doubt it.
It depends on what you are selling, what precedent there is, common sense - and the judge's mood.
If you have to refund because the goods are shoddy, you in turn go back to your supplier and claim from him.
BTW, I am not a lawyer, etc., etc.