Many thanks, Trish. I was not aware of FreeReg previously and that it showed the father's occupation. (Ancestry does not show occupations in its baptism transciptions.)
I did a blanket search of all * Griggs for 1821-35 and, as you posted, found William, Joseph, and Job on FreeReg (as below). I am pretty sure all 3 are mine.
William bapt Oldbury, Worcs 28 Oct 1821 - father John, mother Mary.
Joseph bapt Oldbury, Worcs 2 Nov 1823 - father John, mother Mary.
Job bapt Oldbury, Worcs 5 Feb 1826 - father John, mother Mary.
In this search, I also found a burial in 1835 at Church St Wesleyan Chapel of John Grigg, which is probably theirs and Amplias' father, as it fits in with the rest of the chronology. The record also gives John's parents' names, Joseph and Hannah.
So, some real progress here. Of course, now I have to decide which is the real family name: Grigg (as per all these baptismal entries at Christ Church, Oldbury, Amplias' at Tipton, in the 1851C) or Gregg (as per her marriage in 1852 when she consent by mark, not signature).
As I say, I am pretty certain these folks are mine, thanks to your help, but I would really like images of the baptismal records in the parish registers. Neither Ancestry or FindMyPast provide images of the original baptismal entries for Worcestershire. Do you know where I might find them online, please?
Of course, the mystery remains as to where Amplias' siblings and mother are in the 1841C. One obvious line of enquiry is to look for Amplias' siblings in the 1841 and see whether mother is with one of them. Thanks, Jackie for the 1841 ref for Job whom I suspect may actually be "John"; maybe not. However, he calls himself Grigg, not Gregg. The issue is complicated however by there being two Griggfamilies and 2 Job Griggs in the area.
Any further suggestions, most welcome.
In the meantime, many, many thanks
Best
John