Aside from a well-equipped bike, repair kit and a weatherproof jacket - all you need for a great weekend is a detailed map of where you want to go and a plan of how to get there.
Ordnance Survey (OS) maps are excellent. They include contours (essential for avoiding punishing gradients), and are in most book shops. If you are going abroad, try Michelin's Serie Verte. Try to keep car, train, ferry or plane rides as short and direct as possible. Should you need one, racks are available from shops such as Halford's, and are priced from pounds 35.
Travelling by train with your bike can be enjoyable if you plan in advance. Most stations are poorly designed for anyone with wheels, so ring your local station for details and firmly persist. Label your bike and insist on putting it on the train yourself. Lock it, but not to the carriage. If staff cannot move it, they may bury it under other stuff.
Ferries are by far the most hassle-free method of transport for bicycles. The fares are reasonable (around pounds 25 per person from Dover to Calais; long-term parking for cars is usually around pounds 12).
Pack sensibly and spread the load across your bike - not your back. Most saddles sold with the bicycle are cruelly lacking in adequate padding, and made narrow to suit men, not women. The comfort of longer rides can be improved immeasurably with padded shorts.
Finally, travel safely and wear a helmet. Aside from the obvious protection a crash helmet provides, it also acts as insulation from the debilitating effects of hot, but welcome, sunshine.