What can I do about my mum repeatedly coming to my house without letting me know ahead of time?

There are other people in this thread giving you grief for even being annoyed at this, but I understand you 100%. Even if she's not coming in to the house, just knowing she can and does show up at any time is enough to make you uncomfortable in your own home and make you feel like you have no privacy. The real issue is that you have communicated to her how you feel and her response has been to completely invalidate your feelings on the matter. "But I want to and I will", ugh. This tells me that she doesn't feel she has to abide by your boundaries, that these may apply to other people but because she's your mother they don't apply to her. Can I ask, these things that you don't ask her to do for you, are they then held over your head in an argument etc. as evidence of how much she does for you? My advice would be to set clear boundaries. Explain to her that this isn't OK and if she wants to be a part of your life then she has to abide by the boundaries that you set for her. For example, I will stop visiting if you don't stop coming by the house unannounced. I imagine she will play the victim, but that's par for the course with this kind of people. My own mother is this way. To people who have good relationships with their mother you're overreacting. To the rest, we understand.