Well, quicker than I thought...some good news, some great news, and some just more confusing news

I see you are both offline, and I'm very disappointed! Coz, Monica, you were spot on

Yes, I got the BC of Alexander Philip:
Born on the 16th December 1875, in the Union Workhouse, Gravesend

, No Father
Caroline McMinn, Domestic Servant - Informant:
Caroline McMinn, mother,
Union Workhouse 14 Chapel Lane, Gravesend (as on cert), registered 4th May 1876
I'll scan in some bits of the BC later, as there is a, maybe irrelevant, maybe not, possible question.
This then confirms, that Caroline was definately in England by 1874. It was 1881 that we found Philip with his grandmother, right? Also confirming then, that it was the right Bridget. I wonder how she ended up in Gravesend. Will check that address in Gravesend, in 1881.
The second cert I got today was the MC of Matilda McMinn. She did marry Henry Heath, and he was a Sergeant in the RA, Matilda was listed as 18, but I think she was younger. Her father was down as Alexander McMinn, but get this, his occupation? wait for it...CLERK! There were three witnesses...2 of them unclear...but the 3rd...Eliza McMinn. Will scan bits of that later too, to get clarification.
Which now confirms, that Elizabeth McMinn was also in England from 1874 at least.