You can also search for used equipment in the internet. There are many websites which feature used equipment for sale. The downside, though, is that you are unable to see the item personally before buying it. Also, there is added cost for shipment, so it may cost a bit more than when it is bought in a store.
What equipment do you need to buy? First, you need a kite. There are different kites available, such as inflatable kites and foil kites. There are pros and cons to each type of kite. It is best that you buy the kind which you have tried kitesurfing with.
Next is the board. Again, there are many different boards available and each type performs differently, so choose well. The board has footstraps which make it easier for you to attach and detach from it.
Other equipment includes helmets, life vest, harness, flying lines and control bar, among others. A wetsuit and some boots complete the get-up.
If you live in UK, there are many sources of kitesurfing equipment. But one word of advice though. Before purchasing any equipment, make sure that you really like the sport. Equipment can be quite expensive, so it is wise not to spend money on it if you have no intentions of pursuing the sport.
Perhaps you can test the waters first by enrolling in a kitesurfing school. If after a few lessons you still feel the same way, then that's when you buy the equipment.