Bit difficult to pick out the layout as you decribe Pheonix. When you say their escape route is through the restaurant do you mean by way of a protected route to a final exit rather than an unenclosed stairway into the restaurant?
How did I get roped into this!?
Anyway, now that I'm implicated, wot NT says...
Suttonfire, you don't quite seem to have got the correct idea of what NT is suggesting. It is not acceptable to have an escape route through the seating area of the restaurant when that is the only route out. However, if there is a way out the back of the restaurant and if that route is completely fire separated from the seating area route to the front then the people making their escape during a fire will have a choice of which way to go when they get to the bottom of the staircase. If the fire's in the seating area then they can go out the back and if the fire's on the rear escape route then they can leave via the seating area to the front. This solution would require fire resisting enclosure at the bottom of the staircase and it is sometimes difficult, in existing buildings, to get this to comply with the recommendations of Approved Document K. Also, as already stated, this solution would require a line of fire resistance through the building separating the front and the rear routes.
Various fire services have (rightly) issued prohibition notices in similar cases to what you describe but they may find it a little more difficult to do this if the sleeping rooms have escape windows. The niceties are all a little subjective but what is clear cut is that it is not acceptable for the escape route from a sleeping room to be through a restaurant (irrespective of the number of detectors or the separation of the kitchen).
Stu