Hi AliG,
I am also in the process of getting our kids British passports,
from what you said, you made a copy of all of your passports, each page? We have 5 passports in total, oy vey!
Also, did you have to send expired passports? I though I read somewhere that you had to.
Thanks in advance! And good luck!
We did make a copy of all of our current passports, every page :\ But I did not include any expired passports, or my husband's US passport (he is a dual citizen). That was my understanding of the requirements, and we got my son's UK passport back with no issue! Well, apart from me having to send in grandparents' birth certificates afterwards, which was my own fault.
Here is a list of everything I sent in the end:
Full color copies of our passports (My US passport, my husband's UK passport, my son's US passport)
Son's Birth Certificate (original)
Husband's Birth Certificate (original)
My Birth Certificate (original)
Our marriage certificate (original)
My MIL's birth certificate (original) -- she is the only one on my husband's BC, if both your spouse's parents are listed you need both of their BC's I believe
Good luck!