Yes, I believe absolutely in an afterlife.
In answer to your question about animals Lonelymum, yes they have spirits too. I'm lucky enough to have quite alot of experiences with spirit and 3 of these involved animals.
The first was while I was working at a rescue centre. I was cleaning a kennel when out of the corner of my eye I saw a dog outside the kennels. Looked up in a panic (was completly terrified I was about to lose one of the dogs, when I saw she was transparant and reconised her as a dog my family had owned. She then disappeared. I told Mum about it on the way home (was only 14) and she told me they'd adopted this dog from this rescue centre before I was born, a fact I hadn't known before.
The next was a dog we fostered. While in our care he passed away from cancer. A couple of weeks later I was sat on the sofa at home. This dog had always had a habit of pushing his nose under my hands when he wanted to be stroked and as I was sat there I felt him doing that.
The last was very recent. The day after Dd was born our cat dissappeared. We had thought he'd gott he hump and was sulking. I was changing Dd a few days later when I thought I saw him out of the corner of my eye. I looked up and called his name, and he vanished. I thought I was going crazy but found out from a neighbour a week later that Mac (my cat) had been killed on the road and that they'd taken care of him. I'm certain that what I saw was Mac's spirit coming to say goodbye.
You may think I'm crazy (it's quite possible) but these things happen all the time.
Also in answer to your point about the amount of spirits there must be in the afterlife I personally believe reincarnation, but that's a personal belief.