does it require a visa??

AIR China has cancelled our flight, so now we can't continue to Cambodia 5hours after we landed in Beijing, it will be now the following day evening. arriving to Bijing at 12.05pm and next flight is only 18.45 the next day. Do we need to have an entry permit for this short period of time and can we leave the airport to sleep in a proper hotel!? Thank you very much for fast answer!
We are Slovakian and Hungarian citizens traveling from London to Cambodia through Beijing.