Hello, I don't know if you have already been on your trip, if so I hope you enjoyed it. If not then the advise here is pretty good.
From my trips around France, Spain, Ireland and of course the UK I found there are a few essentials.
Breakdown cover (I broke down in Ireland, so needed recovery back to the UK and home)
Puncture Repair (those tins that squirt something into the tyre, just to get you to a garage somewhere to get it replaced, again needed that in Ireland on a different trip)
Phone with power bank (so you can call said breakdown services)
Wet weather gear (hope you don't have to use it, but if you do they are essential)
And for those very long trips, a spare key (I haven't had to use it but my friend has, and if you ever go on a European trip with friends have your friend hold your spare key and you theirs)
AS said on previous post, I would not have anything on my back, putting it on in the garage, kitchen or lounge for a few minutes it'll feel fine. After a few hours on the bike it'll feel like you have rocks on your back and it'll knacker you out. Get a waterproof bag and bungy it to your passenger seat.