I helped a friend with an itinerary last year (Summer 2018) and this was the list of hotels to be considered. I still have a second list with a few extra hotels but would have to find it.

The following suggestions are for an itinerary where you would skip Colombo (which is quite fare from the airport) and drive up to Negombo right away. This allows you easy access to the Golden Triangle.

CMB-Negombo:
Lagoon Resort Sri Lanka | Jetwing Lagoon Negombo | Official Site

Not a luxury hotel but Geoffrey Bawa design and there's not much luxurious in that area anyway.

Golden Triangle, Anuradhapura
https://www.ugaescapes.com/ulagalla/

North-East coast, Trincomalee
https://www.ugaescapes.com/junglebeach/

Golden Triangle, Sigiriya
The Elephant Corridor - Luxury hotel in Sigiriya

Kandy
Ellerton | A boutique hotel high in the hills above Kandy

Hill Country
Bungalows in Sri Lanka | Tea Trails | Luxury Holiday

Yala National Park
https://www.ugaescapes.com/chenahuts/

Yala Hotels | Wild Coast Tented Lodge Yala | Official Site


South-East coast
https://www.aman.com/resorts/amanwella

Weligama Hotels | Cape Weligama | Official Website


This itinerary ends with a few days on the beach but you could easily add Galle (Amangalla) before heading back to CMB.

Transportation: private driver, train Kandy-Ella or vv (a well-known and rather iconic journey), Sri Lankan airtaxi - Cinnamon Air.

Let me know if you would need any further information.