To AGN & VW, many thanks to you both for the informative responses above.
As AGN pointed out once someone gains that citizenship by descent - then there is no-way to pass it down one or two more levels, unless of course if one asked to rennouce British citizenship (& was granted) then starts the process all over again
1. Marry a Brit, take up ILR, stay 5 years then naturalize
2. Apply as a commonwealth citizen with a certificate of entitlement - which may or may not happen - stay 5 years & apply for naturalization.
By rennoucing British citizenship after getting it by descent - then 1 & 2 steps above is not advisable IMO.
Once someone has descent & a Brit passport - keep it, its worth the paper its printed on.
AGN, personally, I have found the British citizenship route by descent to be discriminatory ... male vs female - registration vs naturalization
For my wife her route via UKM was 30++ years of headache & heartaches.
Me being a
UK born male, has passed British citizenship down through descent to my two kids, which leaves only one more step before the linkage to British citizenship is broken, unless they [my kids] live in the UK & have UK born children.
Funnily enough, my Canadian born [British citizen] daughter is engaged to a Canadian born who at present has no lineage or rights to the UK or any of EU countries.
He can ride the coat tales of my daughter - apply for a partner visa, then hopefully qualify to granted ILR - enroute to becoming a Brit through the naturalization route. Should they get married [hopefully], live in the UK & have children there - it then provides for two [or is it three] more minimum steps by descent for continued British citizenship by descent
Disclaimer: I am not an immigration expert & anything that I post on visa & immigration is based soley on more than 30 years of personal experience & interaction with the UKBA & Home office.