To end my relationship to concentrate on my daughter.

[AutumnHibernator]

My exH has split up from his girlfriend and as per usual he's back dating again within 2 weeks of the split 🙄

Anyway, he's now brought my daughter home early 3 times or cancelled having her in order to go on a date.

I'm in a relationship which can be emotionally draining and demanding to be honest, my daughter is completely aware of why her Dad is not having her as he tells her, as if she'll be excited for him! She's clearly feeling a bit lost and emotional about this, and I'm wondering if I should just end my relationship in order to completely focus on her and be stable for her sake?

Yes, I would.
She deserves to be put first, these years are so important for giving her a secure foundation to build on, she'll need the extra support when her dad is flaky.
Well done for considering this.
You'll thank your future self.

Thank you to those for the kind and helpful comments, I really needed to read those. After a week of him organising all our free time to spend with him and his kids by booking things and surprising us I've reached my limit, I just want to be with my daughter.

Emotional problems left to fester in children invariably become massive in the teenage years and harder to solve.
You will be left to navigate this.
Also you are coming across as feeling very dominated and powerless in this relationship with a controlling man.
Think what you are modelling to a child with difficulties and a useless father.

Controlling men don't care what you want or your daughters needs, its 100% all about them.
This is such a bad environment for your struggling child.

Single mum here too and the one time I dated the bf said "you always put your kids above me!" as if that was a bad thing. He went in the bin. Most men don't get that they don't become your primary reason for being just because you share a bed with them. I haven't dated since and so many friends are on about how I should "get back on the market" etc - like I'm a frigging cow being sold. I don't want it! I want to enjoy my kids, be a mum to my kids, make a nice home for them. I don't want to be going through the faff of dressing in suspenders on my 1 night off so some porn prepped goon might have sex with me, then might deign to stay. Why? So he can take up the last remaining free time I might have and make my house a mess? So overrated.