Wow that's excellent advice everyone, thank you.
I can see that I was obviously wrong to want a cat (after having had one for 20 years I guess I don't really know what I am getting myself into). What I really want is a pet that can't look after itself, needs walks because it's too stupid to go out by itself, can't clean itself and so your house smells (or you spend a lot of your own time washing it, fun!)and is harder and more expensive to have someone to look after it when we are away on holiday (cats just need someone to feed them, don't need walks, to be let out for the toilet etc)
Thanks all, you've convinced me.