Yeah, I think handing in the new NBI will be the best bet. If they get it after deciding then no loss, if they get it before, it should mean they can't turn around and request it with another bring-forward date. My wife ordered and paid for it but it won't be ready for pick up till Aug 1st, so there is still a bit of a wait.
I think I will add your (CJGs) points to the email I am working on. Points 1, 3 and 4 I think cover most of it. My take on point 2 when I was talking with the MP's official was that if I hired anyone, like say, a plumber to fix a leaky pipe and he said 2 days, then I expect the work done in 2 days. If the next day he says 5 days, and then 12 days, then 6 months, well... most people would FIRE that plumber. But of course there is no way to fire immigration because there is no competition (and outsourcing would not fix THAT). And of course there is no agency to force them to do anything if they want to drag their heels.
I also asked where I should I address a letter calling for the creation of an ombudsman for immigration. She said to send it to my MP and he'd get right on it. Ummmmm-no, I don't think that is the right answer. I guess maybe the opposition critics and leaders should get that one. Considering this governments secretive ways I don't see them implementing something like that anytime soon.