thanks to everyone for the helpful comments along with this really good tick list of things to do. The main thing I have learned is, I don’t have the patience to do this so I am taking my macbook pro (early 2013) 90 odd miles to my nearest Apple store with a Genuis bar. They can sort it for me. They might charge a lot to do it, but at least it will be them risking messing the process up not me! Thanks again.
by a plastic card, do you mean a credit card type thing? thanks in advance.