Change of Surname in BRP

Hi,
I couldn't find any relevant posts hence posting as a new topic:

We ( I, wife and 2 children) are Indian passport holders with ILR status for all of us. I took a decision to change the surname of my children and got the new Indian passports with changed surnames.
Now I need to change the BRP of my 2 children with the changed surnames.

My questions are :

1. Which form I should use for the change of surname ?
2. Since there is no change in details of the main applicant ( me) should I submit the forms with only dependents details. ie; filling the details of my children only in the application?

Gov.uk site directs me to fill form NTL ( https://www.gov.uk/government/publicati ... k-form-ntl) for the new BRP with a fees of £260/- per person which is too high for a surname change. Hope there is a different process ith less fee for the same service.