Letters of consent are often held with church records. I wonder if the original church record, St Davids, Surrey Hills, might include the letter.......with address of writer, mother Alice.
Alice Phillips is alive in 1902, but not present at the marriage of her very young daughter?. Who has Alice been living with......brought up by?. Is there a residential address on her marriage cert?
Alice is probably all of the names - Harrison and Corbett and McCormick..... because of domestic arrangements...she was a married woman but William Phillips was not her husband, or Alice might have assumed family name of her stepfather when her widowed mother re-married etc.....all possibilities.
What details do you have on the marriage certificate for Ernest 1905.?
Who is the third child you are considering in this family please?