Hi Sham, I think you don't give yourselve enough room in front of the sinks (would be only 40cm). How about like this:

If am of the option that there are a couple of cues to the minimum size. If the room size is: 4m wide x 5m long x 3m high -equals 60m cubed- therefore light fitting minimum 60 cm diameter with 60cm drop. The room can likely take a light fitting that is twice that drop and diameter. Also the ceiling rose is a good indicator- The light fitting room will look too small if less than the diameter of the ceiling rose. The height or drop also depends on the situation. So you must be able to walk under the light fitting unless this is over a table in which case the light fitting can be lower.

Ditto re very good sized bedrooms. The only thing I would consider is if you could squeeze in another separate shower or at least a wc up there if you have 3 doubles sharing one bathroom? I guess it depends on how many rooms are permanently filled and also if you have any downstairs facilities

Any idea