Well, bumprs arrived today, along with the promised screen protector and even a polishing cloth.
The quality of the bumprs isn't quite what I'd hoped for, but for the price I don't think I could really complain. Here's a summary:
The 'black' case is more of a translucent grey.
The white case just has holes where the buttons are, it's not so easy to press the buttons.
The black case indented bits on the case so if fits over the buttons, so they're a little easier to press, but still not great and it greatly reduces the tactile feedback so it's hard to tell when your actually pressing it.
The white case has separate dock and speaker holes at the bottom, the black case just has a big hole for all.
They're pretty flimsy, and I'm certainly not going to do a drop test with them.
I wouldn't say they're a bad fit, but they could fit the iPhone better.