How many children didn't have their birth registered with GRO in the early years of registration?

I'm frustrated in my research of the Hamilton family in Islington, London, by the lack of birth registrations for John 1838, Eliza 1841 and Charles 1844, all appear in the appropriate census ('41,'51,61) along with older siblings James and Mary Ann born pre registration. I have found a baptism and burial in 1841 for Eliza*.

My frustration is that without the birth certs I cannot find the mother Mary Ann's maiden name. To compound the situation I can't find any marriage for her husband John (senior).

*Eliza's baptism seems to be outside of a parish as the heading of the register has been altered to 'All Saints District, Islington'. The first page in the register is also altered to 'All Saints District, Parish of the Holy Trinity St Mary Islington'. Phillimore shows Holy Trinity and St. Mary as two separate parishes. Eliza is buried in New Bunhill Fields Burial Ground, Islington, a non Conformist burial ground.

Am I dealing with a non-conformist family who decided registration was not for them?

Any comments or suggestions gratefully received.

 

This baptism was in a parish, and a district church is a bit like a daughter church, and may become a parish in its own right in due course. So the parish here is Holy Trinity, Islington and the district church was All Saints, Battle Bridge.

Phillimore tends to focus on parishes which were established by the early 19th century and doesn't include later parishes.

 

There is a marriage of a John Hamilton & Mary Ann Bryon in Islington in 1832, so have you followed this one up?

I notice also that there is a birth of an Elizabeth Hamilton mmn Bryan in the Brentford district in 1837, and a possible burial for this Elizabeth in 1838.

I didn't find any other Hamilton-Bryan births (& variants) but I notice that Charles was born in Brentford, so I wondered if this might be worth following up - if you haven't already.

 

Many thanks for your help Pauline. I will certainly look into your suggestions. This may be the missing link in a DNA trail to a possible cousin in New Zealand.
Thanks also for the explanation of the 'daughter' church. I hadn't realised that Philimore had the emphasis on the earlier records, something to bear in mind for the future.

 

Thanks again Pauline for spotting what I had missed.
I've not ordered the birth cert for that Elizabeth yet. But the town of Brentford rang a bell. I'm wondering if the Grand Union Canal (Paddington Arm) comes into this puzzle somewhere, it's about the right time, and it links Islington to Brentford. Being a navvy (labourer in 1851 & 1861 censuses) probably paid better than his 1841 occupation of 'Waiter'. I doubt we shall ever know, but I think it is worth keeping in mind.