Mel, I'm hopeless when it comes to resisting baby stuff so we started getting things quite early.
Seeing as you already have the cot and change table, maybe get a chest of drawers to match. Then you'll have the basic furniture.
After that I made a list of everything I wanted to get and we just worked our way through as we saw things.
A pram and car seat are probably the other big/pricey items so I'd start with them and you can lay-by if you need to with plenty of time to pay them off.
I bought a great magazine called "Buying for Baby" that had pretty m uch everything you need in it, with prices and product comparisons. Very useful.
For clothes, bedding etc, we waited 'til we knew what we were having then bought the appropriate colour. We're pretty much done now, just need to get a monitor, breast pump and some bits and pieces!
HAVE FUN!!!