Early this year I started a job as a contractor.
Originally my contract was only supposed to last until October but it was extended to the end of this year.
It's been an odd working environment, in general the permanent staff are from a small town, most have known each other for decades, they seem to know so much about the lives of their colleagues. It's very gossipy. In any situation I don't like bitchiness and I don't want to be involved. This was only ever a temporary role for me.
When I'd been working there for a few weeks 3 female colleagues started to ask me to join them at lunch.
I'll call them Helen, Sarah and Jenny.
Helen and Sarah have known each other since their 20s, we're all in our 40s. They rarely kept in touch until they started working at the current place 5 years ago.
All 3 of them are permanent staff.
They seemed nice to begin with and conversations were just general chat.
Then when either Helen or Sarah weren't with us they would talk about each other.
Examples would be:
H said that S had an affair, causing S to divorce.
H doesn't approve of S around men because she 'loses her head', is 'slutty' and becomes fixated on men 
S doesn't like H's DH, S says he is controlling and she's pissed off with H because she complains about her DH but doesn't do anything to LTB.
When Jenny wasn't around H&S would talk about how sorry they feel for J as she is generally unpopular at work and then go on to list all of the reasons for J's unpopularity 
As best I could I distanced myself from them and their drama but they've kept trying to draw me in at work and by messaging me outside of work.
H left for another job in the summer, she messaged me occasionally and I kept things light and chatty without seeming to be rude.
In passing I had mentioned a wealthy friend of ours who is single because me & DH had stayed with him one weekend. He lives some distance from us/workplace.
After weeks of avoiding her at work S messaged me to ask me to arrange a date with the wealthy friend (!) I politely messaged back to say that I thought he had recently met someone. S has been unpleasant to me at work since this and has made a point of saying untrue things about me to other members of staff, I know this from the things people have said to me.
I've been hoping to get through my contract and leave without engaging or falling out with any of them.
Thing is that they are very persistent. I hadn't told them but I've been on planned annual leave this past week.
They've assumed that I've left my contract early so, sensing gossip they have been messaging me at least once a day every day.
I'm back at work on Tuesday, after this coming week I'm working until the end of December. I'd already decided to leave even though the employer has offered extended contracts to temporary staff who want them.
Again, S, H & J had been messaging me to know whether I will stay or leave.
It's ridiculous, we're all supposed to be adults.
They know very little about me. I've done my best to stay away from them whilst honouring my existing contract. I don't feel that I can tell them to piss off.
I'm not answering messages or engaging, other than in work conversations, but how can I keep away from them whilst maintaining professionalism and politeness for the rest of this month, especially as they have upped their ante?