PBS Dependant and surname (BRP) change

Hello members,

I am currently on PBS Dependant visa, and I need to renew it one more time before I can apply for ILR.

I will be getting married to main applicant (I received PBS dependant visa as unmarried partner) 45 days before I apply for my visa extension. I will then change surname to his surname. This brings me the my question:

Since I have 90 days to report BRP change of surname after I change it, and since my BRP will be expiring 45 days after I change my surname (meaning that I will probably not break any law if I don't change it before it expires anyway), do I have to change BRP first and then apply for my visa extension or I can apply with my existing BRP (which at that time will have my old surname and my passport will have my new surname)?

I am worried that if I have to change BRP before applying for my new visa it will not arrive in time for me to apply for extension.

Finally, if I can apply for new visa with BRP that has old surname (change happened 45 days ago), should I write a note to the case officer and should I pay any additional fee?

Thank you,
Jovanna