TrevC said:
Use the freebies. No outlay and identical sound!
'Non believers' like you and I are probably better sitting-out these type of threads. I've found that generally people don't want to be told they're mistaken, unless they specifically ask 'is this a load of tripe or is there something to it'. While we might be trying with our best intentions to stop them making [sometimes very expensive] wasted purchases on the assumption that they genuinely don't understand, I've learned it's not the message they want to hear and it rubs their fur the wrong way, no matter how you say it.
That said, for £18...I'd give it a shot, even if it's just buying you better build than the standard cables.