Seems quite normal question.
When you have family or friends from over seas then you must fiil out a form signed by your flat mates so that they are ok by you having visitors, you can only bring max of 2 people at the same time and for a period of 2 months I believe, so, when the form is filled up you give it to the security guy downstairs and accoodation looks at it and within a few days they give you the answer of wether is accepted or dennied the aplication.
As per the rest of the crew no one minds because most people visiting the flats are crew themself, so they can stay.
Some buildings dont have security and therefore they don't have corfew, (don't ask), but those buildings are very popular je je je
.