Oh there is nothing more annoying to some than someone working part time when they (have to) work full time! And if you don't have kids they can't fathom for the life of them why you don't work full time.
Since I retired several years ago, shortly before I was 50, I have had judgy, rude, sarcastic comments from many people close to my age (45 to 55.) One woman (aged 54,) in my neighbourhood, is incensed that I don't work, and keeps asking why. What do I do all day? Don't I get bored? Surely I will work again ONE day?
FFS, I worked for almost 35 years, and paid my dues. I was a high earner for much of that time, (professional career,) and paid shit loads in taxes and national insurance. So when the chance to retire came up at 50, with a good pay-off and a good personal pension, I grabbed it with both hands.
I get people asking 'well are you and your husband ok with just one wage are you?' and 'are there medical reasons for not working?' and my personal favourite 'are you ok with being kept by your husband?'
Errrrrrm I am NOT kept by him and have my own income thank you! All kinds of bollocks questions. So annoying.
I get envy, confusion, and pure, unadulterated bitterness and jealousy.
I worked part time before I had kids too (just for a year as the company was making cutbacks and asked for volunteers for people to go part time,) and again, I got so many nasty, sarcastic comments. I also went part time (24 hours a week,) after having kids but didn't get as much shit then.
At the end of the day, it's got fuck-all to do with ANYONE if you want to go part time, or even give up work altogether. It's their problem, not yours.
As for whether the company you work for would have an issue with it (not inviting you to stuff, telling you to not go to meetings etc,) that would depend on the company of course. Never happened to me though. My boss/the company were OK with me. Although a couple of colleagues were sniffy with me sometimes. I put it down to jealousy.