It's great to get a question from a fellow Brit Joanne, I hope I can help!
You'll be pleased to know that I've used the Disney Dining Plan several times and I got it for free too which made it even better! Firstly I recommend you take a look at this link
HERE, it is a pdf of the 2009 DDP brochure and it explains how the plan works and lists all the participating restaurants. Next I would try and make a rough plan of which restaurants you'd like to try, have a look at the dining pages on the main Disney website or look at
www.allears.net as they have great menu pages. My favourite meals are Teppan Edo in Japan in Epcot, Kona Cafe at the Polynesian and Narcoossee's at the Grand Floridian. On 2nd July you will be able to phone and book your reservations and I strongly recommend you do, the number is 001-407-939-3463. But I have found a number which only costs 1p per minute instead of the international charges, it is 08448-610-610 then when prompted enter the dining number.
On arrival at Animal Kingdom Lodge, great choice by the way, you will be given your Key To The World card which will not only act as your room key and park ticket but also will contain all your DDP credits. One thing to remember is you can spend your credits in any order you want, we always book at least one 2 credit meal (it shows which ones are 2 credits in the pdf) as we are always too tired to eat a proper meal on our arrival day so have a "spare" credit. Oh and snack credits can be used on a huge variety of snacks, the general rule is any single serving item under $4, we love to buy funnel cakes in Magic Kingdom or ice-cream sandwiches from the MK bakery!
Any more questions please ask away, I hope you have a great trip!