This depends upon the geographical location and indeed, the amount you're spending. I'd definitely use my Amex for items over £100 (for Section 75 protection)

This depends upon the geographical location and indeed, the amount you're spending. I'd definitely use my Amex for items over £100 (for Section 75 protection) but under that amount my understanding was that you're reliant on the (voluntary) chargeback scheme which I can use with my bank and debit card too. So the only thing you really gain for the smaller purchases is the money not leaving your account with the CC, I think?