Hi Karen,
I have spent quite a long time going back over this family and I am no further forward with it.
Did you ever ask the Bristol Records Office for the details of Robert and Elizabeth's marriage? It may not have the father's names but should have the witnesses which may throw more light on the family.
I see you have a baptism for Frederic Lloyd but I don't think that is right as there is another Frederick Lloyd in Water's Lane, Bedminster as shown on the 1841 census whilst your Frederick is at Howards Green, St Lukes, Finsbury with his parents and siblings. George and Elizabeth were baptised at St Philip and St Jacob Bristol, so would imagine that Frederick would be baptised there too as we know he was not born in Middlesex so chances are he was born in Bristol and the family moved soon after, to London. Perhaps it was after the death of Elizabeth, maybe in childbirth so a death entry close to Frederick's birth may be relevant. There are a few in Bristol but nothing that jumps out immediately. I cannot find Frederick or Robert in 1851 though.
When Robert married Martha Burman, it was stated he was a bachelor but when he married Mary Phillipson he was a widower. So is this the Robert that was married to Elizabeth, 1841 indicates it is.
It is all very confusing.
It looks as though Elizabeth Aiken remarried in 1873 after the death of Henry in 1872 but I have not checked that out. He left her well cared for in his will.
Sorry I have not found anything new for you but it looks to me as though the family in Bath is a major contender.
Best of luck with it all,
Elizabeth