In your experience, do the cafes at the first two controls take cards or cash only?
AND, since the first cafe' is "receipt from the till" rather than stamp on the card, nobody is stopping me from going to the garage/supermarket instead if there is a big queue, right?
In previous years Honey Cafe (first control) have happily given receipts for £0.01 even if you don't buy anything, but they also set up a counter especially for those wanting quick service of just a hot drink and no food.
I confess I took the penny receipt last year, but then detoured to give them my custom in more relaxed fashion on the way south.
They do take cards - but may have a minimum charge.
Not sure about Llanidloes, cash is probably easier if you are in the 'bulge'. Last year they were set up for quick service in the back yard of a limited selection of items, but I doubt they'll have card machine out there, even if they can accept them inside.