British Grandmother. Am I British Citizen by Decent?
You are definitely not a British citizen by descent because even if your mother is one because of her British born parent, she can’t pass her citizenship to you. You are however eligible for a UK Ancestry visa because your grandmother was born in the UK – the fact that she is deceased doesn’t make any difference as long as you can prove that she was born there. An Ancestry visa gives you the right to live and work in the UK for 5 years, then you can apply for ILR and a year or so later, you become eligible to apply for citizenship. Ancestry visas will probably become unavailable soon, so you should apply ASAP.
British citizenship doesn’t pass down as far as a grandchild. Its the Republic of Ireland that lets people claim citizenship from their grandparents. The UK doesn’t allow this. Citizenship in the UK can only be passed on by parents. Your mother could claim British citizenship from her mother. Don’t think she can pass it on to you though as its inherited ctizenship and I don’t think that can be passed on. It would end with your mother. However: If you live in a Commonwealth country you can apply for a UK Ancestry Visa with a British grandparent. This allows you to live and work in the UK. You could apply for Indefinite Leave to Remain and then British citizenship after several years of living and working in the UK.