MIL driving me mad-help!?

[Josie45]

Ok so I'm new here and not familiar with the abbreviations so bare with me.
My partner and I have been together coming up 2yrs, living together in his house for almost one. We get on fab, he has 6 children from 2 previous relationships and no problems there we all get on great.
My problem is his Mother, she's one of those Mothers who has never liked any of my partners or his brothers wives/girlfriends, and is constantly trying to..... well I'm not sure really either upset me or wind me up. I've tried to explain certain incidences such as her calling me his ex partners name and bringing me his exs slimming world books with her name all over as just errors or oversight. But she insists on talking about his exs all the time, particularly the most recent one, and bare in mind she didn't like her, the thing is she only does it when he isn't in the room and it has happened that many times it's clear shes deliberately doing it when hes not there. There are other occasions when she will say things to him(in a joking way) like do you remember when you two used to.....and go on to share irrelevant memories, which I feel she does to make me feel uncomfortable. She is very close to him, has a key for the house and will call round when we're not in to do gardening jobs etc, she has done a heck of a lot financially for him and deep down I think probably the root cause of her doing this is jealousy as she feels I'm stepping on her toes.
Help, how do I handle this?
I have mentioned it to him but he just doesn't see an issue, possibly because most of it happens when hes not there, but I do feel it's starting to cause a barrier between us.

I think you need to discuss how it makes you feel when she says things like the examples you give and see if you can agree on some boundaries that would help.

She probably did exactly the same thing to his previous girlfriends if that helps any.

Maybe have a heart to heart, and tell her how uncomfortable she makes you feel when she talks about the exes like this.

Thanks guys, I kind of feel she'd get a kick out of me admitting its bothering me and try to twist it against me. She's 80 but quite childish, it's not just me she tries to wind up, she even bickers with the kids on occasion. Not that I would ever give an ultimatum but I know I would never win over his Mother.
Yes I think shes definitely done it before, shes told me the ex would be moody and sit and not talk to her, I wonder why? Lol. Plus when i have mentioned it to my partner he plays it down big time and goes quiet, i suspect this is because hes concerned that past issues may be arising again and doing the typical man thing of if i ignore it, it will go away.
I've tried the whole ignoring it and engaging in the conversation to try to show her I'm not bothered(like you would with a bully in the school playground) but the truth is she makes me feel really pushed out of the family, the fact that said ex is 5yrs younger, extremely attractive and never off the phone(usually all child related) doesn't help.