Having sized people for UKs (though not as many as Arrogcow) I can say its the rare man who can wear his pants size as his UK size (although I have seen it.) At least two sizes up or more is the norm (mine are three sizes up).

As to where to wear it, I find that if I try wearing one at the navel, it slides down to my hips (where it was designed to be worn).

Sizing your first UK can be tricky, so I would definitely take up Aarogcow's offer of assistance.

Best regards,

Jake