Hi
Yes the problem is sorting out which Mary Ann/Marianne Street is the mother of 'your' George. I had 'go' at this yesterday.
I checked for Mary Ann (etc) of the right age in the area of Henley in the 1841 census and found 2 in Ipsden which were the daughter of James & Mary Street aged 5, and the daughter of Jane Street aged 4.
I think the servant you have found in 1851 in Ipsden who was born in Benson, would be the daughter of James & Mary, the house where she is working is only 3 houses away from where they are living in that census. She is with them in the 1861 census, she married in 1862 in Ipsden to William Green - I have a copy of the transcript. So not her in the workhouse.
However I can't find a candidate for the daughter of Jane Street/Woodard anywhere else in 1861 at the moment.
The one thing that bothers me is that the eldest child in the workhouse with M. in 1861 is aged 10 and I would have thought should have shown up on the 1851 census, perhaps she was very pregnant - which is another possible reason she might be in her mothers house in 1851, I doubt she would be working as a servant.
I don't think the one in 1871 who is giving her birth place as Essex is the right person - it is not an uncommon name and I think I can see this one in 1861 already in London
There were 3 marriages (no deaths) for Mary Ann Street in the Henley district between 1861 and 1871
the first in 1862 to spouse William Green - I have mentioned above.
The second in 1869 spouse William Tranter - I have found this couple in 1871 and Mary Ann was born in 1820 in Buckinghamshire - so not our lady.
The third in 1870 spouse Job Greenaway, this one is interesting, Job was born in 1844 in Stoke Row Ipsden, the same small hamlet that all the Ipsden Streets that have been mentioned come from. I can find him in 1861 working away from home as a labourer, but then I can't find him again after that. His birth doesn't seem to have been registered and there is no corresponding death for him in FreeBMD. Did he immigrate?
Anyway - I hope all the above makes sense, none of it is conclusive and most of it is based on the assumption that the family in the workhouse in 1861 is the one we want, which is tricky with no first names just initials. I wonder what records survive for Henley workhouse at that time, the Oxford Records Office would probably be the place to ask.

DebbieG