Before you go check oils, tyre pressures etc. Don't stop in the Coach and Horses by the "O's" ground for a pint.
Charge your phone and top up if you are prepay.
Fill with fuel before you load up. Make sure you can fill up without taking too much stuff off the tank.
Definitely light waterproofs and basic tools
What you need when you get there. Don't forget that you can pick up jeans and t shirts in Tescos for a fiver when you are there. You can also consider posting back any surplus stuff to lighten the load on the way back.
Get recovery (it comes free with some bank accounts so check. and a flexible friend.
Stop when you want to. lots of A road truckers stops around.
I would go Hertford, Bedford, Northampton kind of way.Dont use the A14 or similar roads. A lot are duel carriageways and a chore on a bike.
Longest day ride. From Bol'dor via marseilles, Paris, Dover- Calais ferry, Harlow. Left Marseilles at 4pm. In the shower at home at 6am.