British Citizenship by Double Descent (Crown)

Hi,

I am trying to work out other options of working in UK long term after Tier 5 YM visa expires as I don't qualify for UK Ancestry Visa. I was born in NZ in 1987 and have been looking into crown/designated service of my grandfather to see if it would qualify. He was born in South Africa in 1907, brought up in India then trained and enlisted in RAF 1922-1930 in Bristol.
In 1929 the family moved to NZ and he tried to transfer to RNZAF (which didn't actually exist at the time) he ended up as a Squadron leader in RNZAF 1939 and remained in Air Force until 1958. My father was born 1948.

Father born India 1880 Royal horse artillery
Mother Born Bath UK 1884
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Paternal Grandfather born Greenwich 1861
Paternal Grandmother born Dublin 1857
Maternal Grandmother born Woolwich 1856
Maternal Grandfather born bath 1856

Do you think i have any chance based on the above? Thanks in advance!