Most of the ones out there, the ones by Foxconn, BFG, MSI, ECS and eVGA, all use the nVidia reference design. Asus has the Strike Extreme, but that’s very pricey (over $400 USD). I could be wrong, but the eVGA seems to be the most popular, probably because it’s relatively inexpensive (compared with other 680i) and performs like every other 680i board.
If you think they look the same, you’re right: they are. Go with the cheapest, as you’re not going to be getting anything different besides a brand name. Only Asus and Abit have a different layout, and their prices seem to add an extra £50+ to what you see with the reference design motherboards.