I am flying Air China from Melbourne via PVG to PEK arriving late at night and on the following morning to Tokyo NRT.
I gather that I dont need a visa to transit but can I book a hotel outside the airport? If not are there overnight facilities airside? I am travelling on a UK passport.

Don't plan on leaving the airport.

If you are overnighting in PVG you can leave. Not PEK.

mcmonster, welcome to FlyerTalk. Please follow as the thread moves to the Travel->China forum. Ocn Vw 1K, Moderator, TravelBuzz.

Per SirJman, if your rest break is in PEK, you have to stay at the airside; it's only PVG where you can exit the airport on transit. It seems as if you are transiting in PEK.

Do you have Gold status with any *A airlines? Or are you flying business class on your CA flight? If so, you can access the Air China business class lounge. The CA lounge at PEK (international side) has sleeping cubicles; I don't recall whether or not it has showers. I need to be possibly corrected here by one of the China experts - I don't know whether or not this lounge is open 24 hours, obviously it would need to be for you to catch some sleep before your final flight to NRT.

I wish people who were not rock-solid with their information would refrain from giving advice. OP, much of what was said above is incorrect.

With your UK passport, you get visa-free transit between international-to-international flights at Chinese airports. All of them where this sort of connection is possible. Connecting in Shanghai (PVG, SHA) you have 48 hours grace period for visa-free transit. Connecting in Beijing (PEK) or elsewhere, you have 24 hours. With this oddball double-Chinese-transit situation where there is a connecting domestic leg, you can still have visa-free transit at PEK. Your arrival/departure times are within limits.

You may leave the airport. Let's repeat this, heck let's shout it out: YOU CAN LEAVE THE AIRPORT AT PEK. I do not know why this misinformation is going about in spades. You cannot just "stay airside" at PEK like you might in many other airports in the world, you will be going through immigration although there are specially signed desks for "international transit" which is where you need to go to show passport and onward boarding pass/itinerary, and get the transit stamp in your passport. Once you pass this point, you can roam where you like, as long as you get back and depart within 24 hours. You'll be stamped out at exit immigration on your way back airside.

You may stay anywhere you wish, even off-airport. The lounges inside the airport I've had conflicting information on, even though I've been in there as late as midnight for a late CA flight--as to whether they are open 24 hours or not. Last I heard it closed 2-5 am. The airside "transit hotel" is expensive and often full up. The "time rate hotels" in each terminal on the nonsecure side are of varying quality but T1 and T3 are rumored to be somewhat better than T2. You buy blocks of hours according to your needs. You can stay at any terminal you want. T1 and T2 are connected by walkway. T3 is on the other side of the runway and requires airport free shuttle bus to go to T1/T2. Walk-up only, they don't take reservations. Nearby hotels off-premises are an option but the nicer newer ones may be poor value for just a few hours.

There is plenty of information on this on the China forum.

Why not? The airport is pretty darn boring, a stark contrast with the city overall.