Gill, was going to reply until I saw the response from Janice:
Hi Gill, I don't know much about lenses, however, if the lens has been faulty and repairedonce under the guarantee and has then failed again, you may be able to argue that it should not have failed and ask for a further repair under the guarantee (It depends when guarantee expired). Despite the fact that guarantees are given for a set period of time, the goods must stillbefit for purpose and should not be excpected to fail shortly after the guarantee expires.
'Under the Sale of Goods Act, goods have to be "reasonably durable"
She is absolutely correct, you are protected twice by the sale of goods act, firstly for the initial purchase and secondly, for the repair that was made. This repair admits that the lens has a fault. It should go back to these two for repair, nowhere else. If it goes somewhere else, then your mate is taking responsibility and will be out of pocket. No matter what the initial warranty period was, this is a faulty lens and the sale of goods acts protects for a time that is proportional and reasonable to the cost and purpose of whatever you purchase. Don't send it anywhere else until you have used up all avenues of the sale of goods act.