Thanks for your reply mate. Sadly it's not the cable. The connection where the cable clips into the earpiece seems to have come loose from the external housing, meaning it slips back into the housing when you try to exert enough pressure to attach the cable. I've managed to bodge it back together by using some snipe-nose pliers, two thumb tacks and some superglue! Doesn't look very pretty anymore, but is working for now. I think I'll have to get a replacement as I'm sure they'll break again soon.
Can't make my mind up whether to go back to some Sennhesier IE80s, or try something new. I recently dabbled in some over-ear sound cancelling headphones - Sony MDR 100-ABN and Denon AH-GC20 - but they were both absolute garbage. Pants sound quality and the isolation was pathetic compared to IEMs. Don't know why I bothered! Kinda want to try some wireless IEMs before I give up on the idea, as not having any wires was lovely - shame about everything else! I've got my eyes on some PSB M4U TW1. I might ask whether it's possible to try them out in store before I waste any more money on earphones that I hate. It's an expensive addiction.