I have a number of McJannetts in my family tree, the latest being my Great Grandmother Alice McJannett 1870 there are a number of siblings. Clapham, Brixton and Kingston are among places of birth. Her father was James Hutchins Mcjannett c1823. I believe he also had a number of siblings. His father was John McJannett I believe he may have been born in Wanstead.
There are a number of variations on this surname such as Jannett, Jennett, Tennett and Mackqennett?
If any of these ring a bell with you please contact me or if you have any information on any of these especially John from Wanstead i would be delighted to hear from you

Karen