What to prepare for a long distance ride (1600km)
I took part in a charity ride from Scotland to Italy in June last year, and that was made a lot easier with the use of a support team to help carry everything. Since you are going it alone, you need to consider quite a lot of things:


Directions


It's fine planning a route, but they often don't go to plan. Always be prepared to make alterations at the last minute. A detailed road map of the area / GPS device is essential for this.
Know roughly where you're going to end up at the end of each day. Plan ahead and maybe pre-book your accommodation. Most places allow you to reserver a room for free and pay when you leave, so it comes at no initial cost. If you don't make it to a given town, find somewhere else to stay. You suggest camping in a tent - although feasible, bear in mind the amount of kit you may already be carrying.

Nutrition


Undertaking long mileage takes its toll on your energy levels, so its important to replace the calories and replenish water loss. You can carry sandwhiches or even pop into cafés, but another alternative is the use of energy gels and flapjacks etc. These are easy to carry and provide enough fuel to keep you going.
Hydration is really important, so carrying water or some other hydrating fluid is essential. Try mixing it with energy drink powder to hydrate and keep your energy stores up.

Spares / Tools


Long-distance cycling takes it's toll on your bike, but also increases the likelihood of hitting a problem along the way.
Carry a set of bike tools such as a chain link tool, spanners, hex keys to help you make adjustments and repairs along the way.
Inner tubes, tyre levers and a puncture repair kit (and a pump!) are also vital. You can always find a petrol station or another cyclist to help, but be prepared and be self-sufficient with repairs.

Clothing

Take a variety of clothing to help with the different weather conditions. There's nothing worse than getting into wet clothes when you could have had a dry set to hand.

Waterproofs

Hot-weather gear
Base layers



If I think of anything else I will add it to the list, but these are some of the main things to consider that I can think of.