Stayed there frequently and Plats always get a great UG.
Gift is always a bottle of Bulgarian Red - a Todorov, which is very nice actually!!
Lounge is on 2nd floor, and plats have access, although nobody ever checks anyway!!
Many people prefer Radisson or Hilton in Sofia, but Sheraton has lots of character and the UG rooms can be spectacular.
Ask for Nelly at reception, and tell her David from England said hi - often she'll move heaven and earth to please you.