Hi Mags,
Not knowing any of the circumstances, it's hard to guess
why the baby was taken to England by your grandparents.
I can think of a few possibilities such as the mother being unable to care for the baby due to illness or mental instability, following the birth. Another possibility is that the parents for whatever reason did not want the baby, perhaps it was not normal in some way or it was not really
their baby, but the illegitimate child of a sister or older daughter that they had been passing off as their own.
If there were no stories passed down in the family, I don't think there is any way that you will ever know the truth.
Carmela