And of course, the trader probably gets his money from the debit card
fairly transaction quickly, whereas when I took credit cards it was
monthly in arrears (two months for Amex I think).

Back in the 1980s, that was about right. But times have changed, and
most credit cards now put the money in the merchant's account the next
day.

If a place offers a discount for paying cash, I'll take it. But here
in the US, other than a few petrol stations, they never do.

R's,
John