Yes, Bbevan P&O do restaurant breakfast, always much more civilised than the buffet, especially on the first morning and the last when the buffet is always chaotic, tends to be for a limited time, though. The Horizon newspaper will say which restaurant and the times, or the cabin steward should know, or reception can tell you. We also enjoy a cold breakfast served in the cabin, good for lazy start mornings.
Teetime once on board its worth asking your cabin steward anything you are unsure about - they know it all! Cruise Critic is definitely a good source of information, your cruise line may also have a FAQ section on their web site. Also worth asking whoever booked your cruise, they often know the answers to questions. One thing we do take, if going on an older ship and if case weight will allow, is a multi point suitable extension lead - cabin sockets are rarely where you want them to be, also helpful for charging multiple items at once. New ships should be fine socket-wise. If its a non-Uk ship you may need adapters as well, but that information should be on the cruise site. It will be lovely, just have fun.