You can fly Ryanair or Easyjet from Copenhagen to London for about $30-35 usd if you make reservations ahead of time.
Beware, their baggage limits are draconian for cruisers. Max 33lbs per checked bag, 12 lbs per carry-on, and they check. $3.50/lb for overweight.
Ryanair actually departs from a small airport across the big bridge in Sweden.