Dayvo's Gatwick flights will be the cheapest.
For Ryanair, minimise the extra charges by booking online reasonably well beforehand, including bike, and do the online check-in as well.
If you get a cheap Dover ferry and ride, there's several days of food and accommodation to pay for, plus a ferry from Denmark to Norway, or train from Denmark to Sweden (there's bridges now) and more riding/food/accommodation.
The Harwich to Esbjerg ferry is expensive (£400 ish), and you've still to get to Norway.