I feel a bit thick for even asking this!
My sons friend has taken up bass and got an Ibanez BTB off of eBay. Somehow he bust the low E string (can't imagine how???). Anyway, he got a cheapo spare from eBay but it was quite a bit too long. He stuck it on anyway and wound on a ton of 'thick' string onto the machinehead rather than the taper, and to cut a long story short, it not only bust the top of the tuning peg, but also the internal gubbins!
So, I'm getting a new machinehead for him, but the string was too long? would I need to order a specific length?