This shows intent to purchase, and is once again in your best interest. The deposits are usually non-refundable. If you are close to the cattery, ask to see the kittens parents. Catteries are NOT pet store's. Just because you can afford a kitten does not mean you will get one.
Most breeders like to interview prospective owners, either verbally, by email, 'phone etc.
They are just concerned with finding their fur-babies the best home they can. Ask for references. It isn't always easy to buy something so special, sight unseen. You want to know the breeder as much as they wish to know you. I hope these tips and explanations help you.