[tamajiv176]

Yes, I think I'm just going to abort the John Lewis one. What's the best method for Amazon? (For a high value item).

That would depend some on your account with them. If you don't have any returns in the past few months, have not had any emails such as "we have noticed an unusually high number of issues/returns with your orders" (and similar),
have used your account for legitimate purchases then you have a few options.

I would probably default to DNA since it is relatively straight forward. Be prepared for the incoming carrier investigation so plan you delivery accordingly in advance. I am certain that with an iPhone 11 pro they will open an investigation if you DNA simply due to the value of the item.
You can try to box them or even FTID (I would not recommend it).

Keep us posted on your progress!

Thanks I appreciate your advice. I have an aged account and do regular legit orders, I did get that email you refer to once, but it was a while back. No returns in the past few months.
Also, you mention "plan you delivery accordingly in advance", what steps do I need to take to do that?