Citizenship Oath ceremony booking after 2 mnths of approval

[Ishwarch]

I really need some help.

I have received approval Letter of British Citizenship from HOME Office dated 20th June.
I contacted my (Hillingdon) council and asked can I book an appointment for Oath Ceremony in September 1st Week. They can give appointment up to 1 month.

My family is travelling to India on 21st July and back on 4th Sept.
I am travelling to India on 13th Aug and back on 4th Sept.

Approval Letter clearly letter I need to book an appointment for oath ceremony within 21 days of receiving the approval.

I called HOME OFFICE today and told them that I have this situation and can I book an appointment in Aug for Sept 1st week Oath ceremony and it’s within 90 days. They said “I need to book an appointment within 21 days, if council is not giving an appointment for Sept, then they cannot help”

I have also enquired with council about Private ceremony booking in September, they said they will have to check with Registrar and then they will call me back.

Can someone let me know? What is the best way for me?