Just a thought re Jane in 1851 working as a servant for a large household in Park St, Westminster 
Mrs Smith - Birth abt 1826 Englefield Green, Surrey
Residence St George Hanover Square, Middlesex
Kay
Yes. I’ve been mulling that one over.
Did you notice Selina Harvey (the niece) was also born Englefield Green
In 1861 she is Selina H. Bathurst Born Egham, surrey, and there is a baptism in 1812 that fits.
And the 2nd housemaid was born Egham. So they do appear to recruit from the area.
There are several Jane Smiths baptised at Egham in the period
1823, John & Ann. John a labourer.
1831, John & Hannah. John a gardener.
I wonder if they are the same couple and 1823 Jane died. (Added, don’t think so, there are two that fit in 1841)
Added. John & Ann had a lot of children baptised at Egham. In 1818 one of them was named
Louisa. There were at least two Elizabeths too, but that’s a more common name.
And.. there are COMPTONs in Egham