Let's consider the example of UK:
Total population of UK - 10 million
Number of tourists visiting UK per year - 36 million (fact)
Tourists could be visiting for work or exploring places. Let domestic tourism for work, medical, family, holiday be 30% of total population - 3 milion.
Total visitors per year - 39 million
For work, visitors must be staying alone in a room, whereas since most of the hotels cater to tourists from outside, they will be residing in pairs of 2 or 3. Let it be 2 persons per room. So that makes it roughly 20 million rooms per year.
On a daily basis, about 55,000 rooms.
An average UK hotel can be assumed to have 3 floors, each floor having 10 rooms. So 30 rooms per hotel.
Assuming that year round occupancy be 60% ( UK being prefered travel destination), so 18 rooms per hotel. (we can also break it seasonly)
so, 91666 / 18 = 5000 hotels in UK