Thanks. You do get a British passport through a father or mother, but sadly not through grandparents - I've looked into it before, and the only thing ancestry that far back entitled me to was a 4 year visa, now extended to 8 years. I can only apply for a passport once I have my indefinite leave to remain (permanent residence), which I'm now getting the ball rolling with - then after living here another year, I can get the passport. But one has to come before the other in my case. It'll be pretty 'automatic' though, I think.