First thoughts were that I had filled the tank up too much and it was being vented via the over flow tube, but then I noticed that the fuel was running down the right hand side of the bike and the vent tube is on the left. I noticed that my bagster tank bag was wet with petrol in the area that meets the seat, so I ripped it off and found the problem - a small weeping hole on the right had side of the tank, just where the knee section meets the seat section.
It seems that my tank bag has (on both sides) rubbed through the paint at the crease/junction and through the metal on the right hand side, allowing fuel to seep out

I'll be having a few words with the Bagster guys here in OZ, as you can imagine!
I've ripped the tank off and propped it up to avoid any more spillage and m now wondering what to do. My gut feeling says new tank or fix, but I am aware that both of these options are fairly expensive but may be the only way to go....
I have put out some feelers via Findapart for a second hand unit but I was hoping that the combined genius (or is than genui?) of this forum may have an idea of something I could do and that would be relatively cheap to do!
Of course, if anyone has a tank for an 03 Z1000 I'd be glad to hear about it!
I should mention that I just moved up to QLD from the ACT and this was the first time I had filled it up since then, the tank was 1/2 full when I got here and I only just used it up. So a temp fix of fixing it up and only running a small amount of fuel until I can get a new tank is not out of the question to keep me running on the road. Of course, a cheap permanent fix would also be cool.....

Cheers!