My v. first thought was Scotland. Zermatt will be in ski season, so lodging will be at premium....though Matterhorn has its visual splendor. How about Denmark with an option of going over to Sweden for a day or two ? You might be able to secure an apt for that amount of time (say, outside of Copenhagen) and do some exploration + photos. I'd consider car rental too....at least for the days of uber travel/mobility. Plan B/C: switch return flight and stop in Iceland for 5 days :>).

Les