Ruch: Sorry for disappearing, I forgot about this and my life got in the way...
The wires inside the cups are still not pulled tight so it's safe to say the drivers are fine, it is a break in the cable somewhere... It may be in the knot as the wire there is already under pressure there - if you unstick the knot and play with it while music is playing can you get sound? The break could be literally anywhere though, if you bend the wire at the break you will get sound as it briefly reconnects. If this is near the plug or earpieces you could just shorten the cable either end - remember which colour goes where on the driver (you have pics, so all good there) or destroy the plug. If the break is in the middle you'll need a new cable.
£40 for the work alone seems very steep and will only get you another weak cable, you might be better looking elsewhere. My offer to have a go at fixing them still stands and I promise to check back this time!