The first thing I realised was that I hadn't been copying over the mbr. So do that - and it fails. Instead of booting it sits there with a flashing cursor.
Right... next! determine whether it's hardware or software. Follow more established methods like using Clonezilla or making a live Ubuntu usb using unetbootin. Same problem...
Argh! I'd spent quite a bit of money on those sticks - 17 of 'em in all (and have ripped them all out of their packaging so a refund is slightly less likely). Right... next approach. Go onto the Internet and see if anyone else has had the same or similar problem.
A few reports of people having much the same problem... Need a solution...
I finally found it. A 30 frustrating minutes later, and I'd tested it. It works! So in case anyone else went down to PB Technology's and brought some quite cheap Toshiba 8 GB sticks, and can't for the life of them figure out why they aren't booting:
It has to do with fdisk trying to guess the disk geometry (why do we still need disk geometry for usb sticks anyway?). You have to specify it's geometry with the following:
fdisk -H 255 -S 63 /dev/[usb drive]
To check if you have this particular usb drive, type in:
lsusb | grep "0930:6544"
It shows up as a Toshiba Corp. Kings DataTraveler 2.0 Stick (2GB) although it's an 8GB - which probably goes some way to explaining why there's a problem.