Looking for advice on British isles or Icelandic cruises

I would like my next cruise to be either a British isles or Icelandic itinerary. I have traveled previously with Royal, Virgin, Carnival and NCL. I am considering the aforementioned itineraries with NCL or Holland America, specifically during June or July. Does anyone have any advice on which company handles these itineraries best during this period of time, or have a recommendation I haven't thought about? TIA.