I'm going to stand with Navy&White here, PIL do cop it quite a bit. Yet I'm guessing if it was DP's it'd be fine no issue. It scares me for when DS grows up as we're close, to think I'm going to feature on MN. You rarely see issues with DD's, maybe the men grizzle at work how they got home and MIL was standing there to great him and stayed for dinner.
It always fascinated me as I have a fair few siblings, so I saw this me time come in. Being one of those pesky relatives who would drop round my Mum's unannounced. But growing up we always dropped in on GP's unannounced. So that's possibly where I got that from. Even now you can turn up whenever to GP's, my Grandmother has never said its my me time, your Grandad is at bowls and I'm putting my feet up.
Usually when I was younger it was me babysitting so my DM could get her me time at the salon then lunch with her friends.
I don't think I've ever had me time, I always assumed after the children have gone to bed is our time to do adulting. Maybe I need to instigate it. Whilst a cup of tea is courteous, anyone would be hard pressed to spring a lunch on me, as we only have what we're going to use in the house.
I won't be posting here about my rogue PIL turning up as they live 100 miles away. So would likely call first as they have no other reason to visit. That's where you're all going wrong, you need to live far far away, then maybe your me time would be platinum protected.
Or another idea, leave a note on the door for the 'postman' had to dash out, leave parcel with neighbours. Then hopefully they'd see the note & leave.