I wouldn't recommend the way you have planned.
1. You can't guarantee the girl you want to spend the night with will be available.
2. You may not able to sleep in and no place to keep your valuables.
You better off finding a cheaper hotel in areas that have many 141s to setup a base of operation then try to bring the girl you like to your own room instead.
http://www.asiatravel.com/hongkong.html
http://www.hotelhk.com/