Abi30, I can understand how you feel, and the fact that your hormones are probably still all over the place may be making the situation seem worse than it is. Your PiL have obviously been very generous and, as you say, you are very grateful for most of the things they have bought. Grandparents can, and do, often go a little bit overboard with buying things for their new GC, so I don't think what you're experiencing is anything ridiculously unusual ... some of us just more carried away than others!
Having become grandparents ourselves for the first time last year, we couldn't wait to start buying things, although we did always check with our DS and DiL regarding any big items, as we knew they would have their own ideas about what they did and didn't want, but again, some GPs can get carried away and think they know what you should have.
I'm sure you've already discussed all of this with your husband, but next time they say they are buying something, and not what you want, tell your husband that he needs to tell his parents that you are very grateful for their generosity, but that there are some things you would like to choose yourselves. If they still want to pay for it, or give you something towards what you would prefer, then let them know you would appreciate it very much. But I wouldn't make a big deal about what they've already done. They are new to grand-parenting, and they are still trying to find their role, and how they fit into all of this. Obviously, you can't have them taking over where your daughter is concerned, but just be aware that what they are doing is out of love.
Can I just ask, what has your relationship been like with your own parents over the past months? Even though you don't live near to them either, do you have a very close relationship with them, visiting them, talking to your mum very regularly on the phone, etc? It's just a thought, but if you are very close to your own mum & dad, and you say your husband doesn't readily share information with your PiLs about their GC, could they possibly be feeling a little, dare I say it ... jealous, or pushed out? I don't mean that in a nasty way at all, but very often, paternal grandparents can sometimes feel a bit left out ... we get a bit of a raw deal sometimes, and people tend to forget that our sons, and new baby grandchildren, are just as important, and mean just as much to us as daughters, and new GC, mean to maternal grandparents. If that's at all a possibility, please, please tread very carefully. The fact that you say you had a good relationship with them before your daughter came along, it would be very sad to lose that, and I can guarantee that they would be heartbroken if you ended up having a falling out.
On the subject of them making comments about you looking fat/being an incubator for their GC/looking better than last time, etc. I agree that those comments were rather tactless, but maybe they didn't really meant anything awful by them. Sounds like it could've been tongue in cheek, and if your hormones were raging during pregnancy I can totally understand why it would upset you. But it probably wasn't meant that way.
Whatever the reason, I hope you manage to work it all out. Be a bit more assertive, and don't let them do things you don't want them to do, but try to be diplomatic. I'm sure they will settle down sooner or later!