Thanks John, you are quite right.
Before I send the jpeg file I send them an email asking for payment and for them to acknowledge a few terms which includes "limited copyright". They agree not to resell the image in any form, not to use it for commercial purposes and to acknowledge Photogenics.co.nz if used in any publication. They can however print as many copies as they require.
Doesn't always work tho. One of the pics I didn't charge for ended up on a guys website and I only picked it up when I googled his name a few days later and bingo, there was my photo with him claiming he'd taken it on a visit to NZ.
Sent him a shitty email and the photo was taken off but I got no reply to my email. Win some, lose some.