Thanks everyone, this really helps.
My thoughts, though not conclusive, are as follows (apologies for not giving credit in each case to those of you who first spotted these facts, I'd like to acknowlege that you've all been awesome unearthing this stuff!):
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A Baker family arrived in 1820 on the 'East Indian' from England in the Parker Party - parents George (age 46) and Ann (age 47), sons Richard (16) and George (13). They seem to have been from Exeter:
https://www.1820settlers.com/genealogy/settlersearch.php?mylastname=BAKERalso here:
http://www.eggsa.org/1820-settlers/index.php/related-records/settler-returns/1954-parker-s-partyA Richard Baker (
https://www.familysearch.org/tree/person/sources/GZZH-9CB) marries Hannah Burnett in 1828 and he is said to come from Devon.
Death records for the same Richard in 1874 confirm first wife Hannah (a child has the middle name Burnett) and second wife (Hendrica Wilhelmina Catharina Hellet). Richard's father is George Baker. Richard is from Exeter.
https://www.familysearch.org/ark:/61903/3:1:3QSQ-G9LS-59WK-C?cc=2573604&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AQLF4-8T34https://familysearch.org/ark:/61903/1:1:2VSM-FWYIn 1828 George Baker of Exeter marries Mary de Visme at English Church, Capetown – the same place Richard and Hannah were married, and George is also said to be from Exeter
Then in 1835 a George Baker jnr marries Alma Engels at the Dutch Reformed Church - he is said to be from Exeter
I'm speculating that the Richard and George from these marriages are the sons of George and Ann who came over on the 'East Indian'
Could the younger George be the same George who married Wilhelmina Jurgensen? I don't think so - a. he married Mary de Visme but also he would have been too young to be having his first child (Elizabeth) in 1822.
There is a 1826 burial at English Church Cape Town (cf. marriages of Richard and George above) for Ann Baker, wife of George, aged 62. I think this must be the mother or Richard and George.
The burial of Mary Baker in 1833 (age 44) wife of George Senior - could this have been George's second wife after the death of Ann in 1826? I can't find a marriage record though.
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the George Baker buried in Seaforth cemetery in 1851 aged 60 looks very likely to be the George I'm interested in as the family generally seem to have been interred at Seaforth which is the local burial ground for Simon's Town
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I also found a baptism for George Baker, 31 Oct 1802 - parents Robert and Margaret Baker, father was part of 34th regiment and baptism happened in Cape Town. Since I can't find any other Baker families amonst the list of settlers which fit with the George I'm looking at, maybe his origins are military rather than civilian? That was listed on the eGGSA site using the baptismal search.
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Of the other George Baker burials on LDS
https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSVY-Y9Y7-Q?i=72&cc=2790463, there is George who died age 72 in 1898, and that I believe is the son of George and Wilhelmina (b.1828, m. Alida) The other two George Baker burials I'm not sure about, but as one is 1886 and the other 1890, I'm thinking that George who married Wilhelmina is likely to be the one who died in 1851. The 1890 death was for a sailor, and George was a mason.
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Where this leaves us is unclear. I think the George Baker who arrived from Exeter is pretty well described in the records and I don't think he's our guy.
Could it be George b.1802? Well the 1851 burial at Seaforth (which sounds likely to be correct) gives his birthdate as 1790, so maybe not.