Aquasea - your instincts are one hundred per cent right! It is a struggle with your first. Maybe your dh and mil are uninformed of the current ethos for new born baby care ?
It is worth noting that our parents' generation were treated very differently when they had babies (They had everything done for them in hospital.) For starters, modern British maternity wards are very different from those that our mothers / mils experienced. If you're going NHS then your baby will be YOUR responsibility from the outset and you'll be advised to feed ds/dd on demand. In my experience, New borns are VERY demanding. I haven't even got started on how you'll feel physically
If you had lived in a huge place (we don't) then it may have been possible to put up with visitors staying, provided they were willing to do loads of work and stay out of your way. In your case though, you'll have jet-lagged in-laws sharing a limited amount of living space with you - and it's amazing how much stuff gets strewn about when you haven't got the time/energy to tackle it. Plus, you'll be wanting daytime saline baths or showers - which may be a problem for the in-laws if they need to use the facilities! (N.B. you bleed a LOT after any kind of birth, and milk leakage makes you want to wash yourself a lot as well.)
It's in dh's and the baby's best interests that you are feeling comfortable, clean and vaguely coping - the overwhelming life changing event of having a baby takes a bit of adjusting too
Luckily my in-laws had already been through it with my sil, so they were not remotely put out by not staying over for a while. After my second, they obligingly stayed with my sil's mil who lives fairly nearby. In fact, it worked out brilliantly for everyone - and we all had a nice time.