Why not just apply for a UK passport and then many other things will be easier. You don’t have to apply for citizenship, you already are a citizen. Why can you not open a bank account? That’s nothing to do with being British, Australian or anything else. You’ll need identification (you have your Australian passport) and you’ll need evidence of your address. Ask your grandparent to phone up one of their utility suppliers (BT/Gas/Electric etc) and add you to their bill. Then they need to ask for a bill to be sent out to them and it will include your name. There you have it, your proof of address. Just google how to find my NHS number or even ask a local doctors surgery if they know how. Not sure what you mean regarding your driving license. A birth certificate is not evidence of identity. It states that on it. Good to have though and hopefully your mum still has yours. If not, easy to get a replacement. Local registers will help although probably all done online now so that’s another easy google search. Add how to get a NI number to your google list. I don’t think you have trouble, you just need to work through a simple tick list to get all what you need. Write a list and tick it off as you get it sorted. Good luck.