when using a header that links you to another site could a wait be added before this takes effect?
or could a wait be added to when a person clicks a link

could be done with javascript, but it will only confuse and irritate people if the link doesn't work straight away.

is it possible to force the browser to refresh?

Yep just create link to "#"

<a href="#">Link</a>

you can use a sleep($seconds) above the header redirect