Hi there,

First of all, well done!

Now, negotiations are quite tricky and it's hard for me to advise here given there have clearly been some pre-offer negotiations.

I'm a bit concerned about continuing to negotiate as my understand from your post is that you already did do this. I.e. you said you were fine with the base salary, then you changed your mind and asked for more, then they gave you more, and now you're again asking for more?

This isn't a great look (again, I think...based on what you've said).

Now, if you want to negotiate, just articulate that you thought the salary would be a bit higher, and, if they could increase it by 10-15%, you'll sign right away. Alternatively, you can try to negotiate on your annual bonus rate, your signing bonus, annual leave/vacation, etc.

Ultimately, the way in which you draft this email (or handle the call) is the most important but it needs to be polite, ernest, and honest. More than happy to help you craft this email or prepare for the call itself!