CrocsUnisex's Crocband Flip Flops

My crocs have always got m 11 on the bottom. i believe that is the us size. what size should i order here, ie uk size?

I have tried these on as a size 6-7 but on here you can only order one size 6 or a 7. Are these true to size or should you take a size up or down?

Do these contain any metal? (i’m looking for hospital mri safe flip flops)

my husband is a UK shoe size 8, has bought cros in the past Croc size men 9 woman 11. Is that correct for him