Long summer tour - decisions on kit?!

[Brains]

I am planning on doing a bit of a pilgrimage from Plymouth to Roscoff and then all the way down through to Athens in Greece.

I would be tackling this during the summer and thus hoping mostly for nice weather.

What would people recommend as the essentials?

I am hopefully leaving in a couple of weeks so need to make decisions on the following:
Sleeping bag or quilt
Tent or tarpaulin
2 or 4 panniers

A bit of context: I am not particularly experienced at touring, however I am pretty fit and robust, having spent the last 5 months in the Army. I don't expect to be taking hair straighteners etc. with me and I am pretty content living in questionable locations.

Any and all advice will be ridiculously welcome!

Thanks for reading

Em

Sleeping bag - it can get surprisingly cold in the Alps in mid summer, and you can always use a sleeping bag as a quilt, but not vice versa

Tent - A small two man one, it means you can camp on sites as well as stealth camp and wild camp. A tarp is fine in woods as a wild camp, it can even work as a stealth camp, but is not going to work in a camp site (which in France the 'Camping Municipals' are the place to go, cheap as chips (sometimes free) and with basic facilities.)

2 x 20L panniers - for your kit, plus a 'click-fix' 5L front bar bag for your money/passport/camera and maybe a lightweight dry bag on the top of the rack for your sleeping bag or tent (tent poles attach to the top tube of your bike with velcro cable ties )
4 panniers if you are taking a full stove and intend on taking a day or two of food with you as wel

3 x waterbottle holders, even if you use one for fuel