Thanks to all who have responded with their ideas. I've been away for a couple of days & will be coding my solution this coming week.
Jeff, I have worked through the examples in the link you provided - excellent stuff, thank you.
I have a 'RoomType' table which I can use as my base table - just need to create a RoomTypeIntervals function to facilitate the CROSS APPLY & see how it performs when compared with the other suggestions.
If you haven't even tried to resolve your issue, please don't expect the hard-working volunteers here to waste their time providing links to answers which you could easily have found yourself.