If you use the spa and nail bar this will use one of your free airport lounge passes. Details of the offers available can be found on the website and the App. You can also check with a staff member before your treatment.
You can just drop in without a booking but you may wish to pre-book your appointment before going to the airport to guarantee treatment. Please contact the Spa direct before your visit. You can log in online or use the App to search for specific facilities.