I made a similar trip 3 years ago, Dieppe / Nederland / Germany / Danemark /
Sweden / Finland(Lapland) / Russian border / Norway (Nordkapp, Lofoten , Atlantic road) / S / DK / D / NL / F . (7500 miles 3 weeks R1200GSA)
All you need is:
A good bike (got it) , petrol was about the same price as France, maybe a bit dearer and petrol stations are nearly every 200 km as max ( never use my extra 3l can) . Fit new tires before leaving,roads are a bit more abrasive than UK ones.
Worm underwear combine (can be use for sleeping when camping). The temperature can drop very low even in june and some place still have snow on the side of the road (this year winter was late and very snowy)but road are clean and dry (sometimes yes sometimes no).Summer gloves and silk undergloves are usefull (i even took my winter ones so you have allways dry gloves). A very good rainproof suit ( and boots) , in Norway you will not have rain allday (well..) but every day you will have a shower (or 2) . On my way up in Sweden and Finland ,i had sometime 23/24° (c) but in Norway the average was 12/13°(c) during the day .
Food is easy to find ,every village have a small COOP .(If you like fish you can bring a small fishing gear (only in sea water)) . Take a thermos bottle with you.
Cabins are comfortable ,but don't arrive too late at the camp site or you won't get one (or only the more expensive ones will be avaliable).
To prepare my trip i went on "nasjonaleturistveger.no" and download maps and details of the site to visit, very useful .Be ready to take sometime up to 7 ferries in a day with different duration of crossings (10mn to 3 hrs) not too expensive.
I'm sure you'll have a wonderfull trip because it's very very wonderful country .
Ride safe and cool.
Roger