Weeelll - the show system in the UK is rather different to the US. No points, for a start. It works on Challenge Certificates instead. In fact, only 3 are required for a championship here. I say "only" because it sounds low (and in some other countries that use a CC system, you might need more like 8) but in fact you've got to beat a heck of a lot of dogs (usually 200-300) to get that CC here, so it's no minor feat.
The other major difference is that dogs who already have championships are NOT separated out from those who haven't. So the only class where you absolutely will not be competing against finished champions is puppies (and they're not eligible to be awarded CCs anyway).
Anyway, dogs and bitches - titled or otherwise - compete in a range of different classes, similar to those in the US. The winners of each class then compete for the Challenge. One CC only is available for award to the best of each sex (and those winners then compete for BOB, and on to group, etc). So I guess the CC winner is pretty much the equivalent to the US BOW.
The reserve (RCC) is for the runner-up and doesn't contribute to a championship. Works rather like a beauty pageant in that respect - you know, the "if for any reason the winner cannot..." (meaning if he's later found to be ineligible, or that someone cheated LOL).
If you want full detail, there's pretty much all you need to know at:
http://www.thekennelclub.org.uk/acti...xhibiting.html