Hi OP - while there may be absolutely nothing wrong and you and your partner are coping fine with baby, I think you've inadvertently and accidentally raised some red flags that HVs are obliged to follow up. The problem is that although you say it's not the case in your circumstances, HVs have seen situations where the red flags have been warning signs of bigger issues so they might be taking precautions. If they ignored the potential red flags and something awful did happen (not referring to your case but just in general), they'd get in trouble for not doing more.
However, if they have told you that there are no concerns when you asked, they should not be insisting on visiting this much. You do not have to see the HV and can call and request that the visits stop. If they have concerns, they should have notified you of these on any of the multiple occasions you asked or if they're monitoring something regarding baby or you, they should tell you what they're monitoring and why. If they don't tell you, how are you supposed to know something's wrong?! If they insist nothing is wrong, they have no reason to be visiting you this much and insisting on seeing you once you'd already cancelled.
It might be the case that as you're slightly younger, they might be offering more support than usual. Regardless though, if they have no concerns you can say that you no longer require HV visits. If you find them useful now and again but don't want to sit for hours talking about things you don't find relevant, tell them you'd be happy for a visit once a month or maybe once every 6 weeks for them to check up on you and baby, without taking up lots of your time.
The first thing to do is call them to engage with their team, explain that you have been told there are no concerns so you don't require the high frequency of visits as they're actually more disruptive than helpful. If they then list some concerns they've had, or suggestions of a plan moving forward, take whatever action makes you feel the most supported and the least harassed.