We were on the Royal in August for the British Isles itinerary. Great trip and the Princess shuttle buses were available for all ports at $4pp. We went on our own in Edinburgh, Dublin, Plymouth, and could have added Waterford. I would recommend the Princess tour to Balfour Castle in Kirkwall but you can probably make arrangements to get there by boat from Kirkwall, which is a charming city to walk around as well. You may want to take a tour from LeHavre. We went to Normandy vs. Paris and had a wonderful and moving experience. If I had it to do again, howerer, I'd probably opt for a cab or van tour arranged ahead of time rather than the Princess bus tour. We wasted hours eating en masse and felt rushed at the beaches and cemetary.
You'll love the Royal. It's just the right size and service and food are wonderful. Go early and stay over in London. Great city to tour on your own. Use the Tube and get anywhere you want with speed and ease.
Take care and good cruising!