In short, Option 3 is the cheapest until you need more than £300 in the EU, or more than £400 outside of it.
I had voted for option 1, based on the scenario that if I go to a cash country (like India or Cambodia) for a month, that this will be the cheapest option. However, having done this sheet, I need to potentially reconsider.
If people would find this sheet useful to put in their own amounts or to check my formulas (which I’m known to get wrong), let me know and I’ll upload it to Google Sheets.
Edit - green cells are cheapest in range
You can have a play with the data here: https://docs.google.com/spreadsheets/d/1NccljGC6nqpyANi3zmSDepAixjLf64gdEXRlXwI4UXk/edit?usp=sharing