My plan re. maternity clothes was just to keep my normal clothes for as long as possible because most of them are kind of loose and/or stretchy anyway. I work at home most of the time so I just wear jogging bottoms and t shirts. I have many jumper dresses and also some dresses like this:
www.hm.com/gb/product/24626?article=24626-C
Also I lost some weight prior to getting pregnant, so I have some things that are a size or two too big for me normally, I'm wearing them now. Obviously this won't be practical for the last couple of months, so I'm planning on getting a empire line maxi dresses as it'll be the middle of summer. A friend gave me some maternity jeans, which I wasn't going to wear, but actually they are awesome. The brand is yesyes but I don't know where they're from. At the moment I'm wearing them with a belt, but they are pretty stretchy and I reckon I'll be able to wear them them until at least 7 months. I have had to buy new pants - I got some under bump ones and one pair of huge over bump ones from Amazon, but I've actually found M&S normal full briefs in the next size up are best, they are big enough to go over the bump for now. Not that it really is a bump, just looks like a big tummy!