I'm only going on our panel, which is perhaps slightly non-standard due to another UK electricity quirk [1], but was done by an electrician last year so is up to regulations at least.

It has a split in the bus, so there are two RCDs, one on the left with a couple of breakers and one on the right with the rest of the breakers, and a separator in the middle.

Like:

    supply in -> R-B-B | B-B-B-B-B-R <- supply in
                 C R R | R-R R R R C
    neutral   -> D-K-K | K-K-K-K-K-D <- neutral

[1] The quirk of our board is that the left hand breaker is driven by a separate supply cable from the meter, which is only turned on between midnight and 7am. In this way, we get cheaper electricity at night which is used for storage heaters and immersion water heater. However, we no longer have the storage heaters, so it doesn't really make sense. This set up is called Economy 7 (http://en.wikipedia.org/wiki/Economy_7).

Also, @alextingle, I didn't know that you were meant to have two separate circuits, although that makes sense. Lots of things are required to be RCD protected in the UK, so as you say, it makes sense just to put everything behind an RCD. We don't get any nuisance trips, which I attribute to a generally higher standard of wiring, earthing etc. in the UK, although that could just be jingoism :) (I did once live in the US and some of the literally fraying wiring connected to two pin sockets with no earthing in the house I lived in scared me.)

The regs in the UK say that (pretty much) every circuit must be RCD protected. But they also say that you can't use a single RCD to protect everything, because you might need power to fix whatever has tripped the RCD.

RCDs are expensive, so the most common solution is to have two RCDs, each protecting half of the circuits.

Anecdotal, but I've had an one RCD installed and have only seen it trip once in about 15 years, incidentally when my old kettle broke (I could reproduce it instantly by turning the kettle on).

Newer installations will often have an the RCD integrated with the regular circuit breakers, so you get one for each branch (as well as one the covers the entire installation).

We typically have a ring circuit each for upstairs plugs, downstairs plugs, upstairs lights, downstairs lights, and then perhaps some special purpose ones - oven, smoke alarms. There's a main breaker for the house, then RCDs for each circuit. Each appliance has a fuse in the plug, and it's not uncommon for the appliance itself to have a fuse in its body.

It doesn't tend to cause many nuisance trips.

Of course, if you buy something from the store and it trips your RCD you know it's got a fault so you return it. And if something old starts tripping your RCD you know it's developed a fault, and you fix it or replace it.