We also did the BIE this past summer and enjoyed a combination of Viking tours and private tours. If you have time, I would recommend taking the train that runs between Oslo and Bergen, beautiful scenery. As for tours, we did a private tour in Shetland (David Malcolm - Discover Shetland), a retired doctor and local historian!! In Orkney we joined another couple and toured with See Orkney, great excursion and were able to see so much more than expected. As for optional excursions, we also enjoyed the Ffestiniog Railway tour, long day, but as others have said, beautiful scenery. This excursion tends to sellout first, but were able to get on the waitlist once on board and it seemed that Viking added an additional bus to accommodate the demand. I would also recommend the Canterbury and Leeds Castle tour. We arrived at Leeds Castle just as they were opening the gates, so for the first hour it was more like a private tour!