Straps?
 

When im playing, I like to play with the bass really low down, like krist novoselic used to with Nirvana, but despite my many hours of trawling local music shops and online, I just cannot find one low down enough!

If anyone knows the name of such a strap, or where in fact to get such a item, I would be very appreciative!

Ernie Ball make long straps.

What's your budget?

budget isnt an issue for me, as long as its not something thats just daft pricing for a bit of leather/nylon haha

Fender makes leather straps sufficient to play your bass by your knees. The cost is about $15.