I went through the process a couple of months ago. Get ready for some frustration 😂.
I was asked to provide a printed receipt from the shop I had bought my SIM card from. The receipt also had to show my name and passport number, a handwritten receipt would not do.
I ended up being quite lucky as I had bought the SIM card to comply with the process and the shop were willing to provide what I needed. A week or so later a friend of mine was not so lucky, the same shop said they were no longer supplying printed receipts and he had to go to an AIS shop on the mainland 😂
Eventually everything got sorted but what a ball ache just to change a phone number on a bank account 😂
Open a Nationwide Flex plus account for £13 per month and get travel insurance for free upto 30 days. To extend for upto 120 days you would need to pay an additional charge, but when compared to the cost of a seperate travel insurance policy it worked out significantly cheaper for me. Existing mediacl issues can also be included, but at an extra cost - of course.