Thanks. I told him that perhaps he needs to spend a lot more in order to get something that actually does what he wants, but he wants to see if the replacement cable works. If not, then he might need to save some pocket money for a while.

Just to finish off this thread, the replacement cable arrived yesterday and it works fine. You simply plug it in, change the audio input selection in Garageband preferences and away you go. I'm not sure it is the best quality, but for 13 quid it is not too bad.

For the record, the seller happily sent another cable, which works fine.