Maybe it would be a good idea to tell your oh that you would like the in laws to visit you in hospital (you will hopefully be helped by the short and strict visiting hours!), and then agree that you would like them to wait a set number of days before visiting you at home?
Avoid unexpected visits - be brave and take control, text them and say "would you like to visit for an hour tomorrow at 3pm?", be specific, then when it gets to 4pm wind it down and say "thank you for coming to visit, it's been really nice! I must see if I can get LO to take a nap now" and take yourself and the baby to your bedroom.
To avoid looking a total mess, I bought some new pjs and one set had black trousers, I actually left the hospital in these as they were so comfy:) I really think its worth buying some 'smart' pjs that look a bit like sports wear/loungewear so you can get up and see people, but you can get straight back into bed once they've gone! Also, just try to have a quick shower, hair wash and face wash etc done first thing in the morning, then it's done. I did feel as though I had made a colossal achievement by managing to wash my hair after DS was born! My friend had a baby at the same time and swore by dry in shampoo!
I personally wanted to get the in law visit over and done with before the baby blues set in, so I had them over on day 3. In the event I didn't get any baby blues luckily. The visit was a pain (literally), they all made themselves comfy on the sofa whilst I had to sit on a wooden stool with sore lady bits - totally same as DillyDolly !
I think with visitors disturbing the dogs and then the baby and disturbing your family time just have to be managed with organised visits really. If it helps my DS slept through the smoke alarm twice in one day :o Sometimes you can get away with it!
I think if you can get yourself to any antenatal classes now it would be good, even antenatal Pilates or something like that as it does help to compare worries etc with people who are going through the same thing. Also after the baby is born, try to go to mum and baby groups, I'm not a great one for socialising, but even a 5 minute chat kept me feeling sane in those first weeks.
Also, do you think it would be worth inviting your in laws out to Sunday lunch or something. It's probably the right time to get to know each other better as they will be part of your life, but they don't have to take over your life. If you got to know them a bit better you hopefully will feel a bit more confident and assertive around them?