Having just come back from a lovely cruise on the Sea Princess, I would like to tell you that just by dialing room service and asking for a pot of tea within minutes the steward arrived with a tray holding a large thermos full of hot water, milk sugar cups and saucers assuring me that it 'was no problem.
Don't know about Sea Princess but there are NO tea and coffee making facilities in the cabin of the Golden Princess. You can get tea/coffee etc anytime of day and night in the Horizon Court. I too was disappointed when I went with Princess to find this. Just got used to nipping up to Horizon to get a drink to take back to the cabin. OR take your own suplies, there is a fridge in the cabin.