Thanks for the help. I got a bit scared by the HTTP_BUILD_QUERY and Dan, if you look at the code you will see that changing the ? for a & will not help, but I found another way of solving this. Maybe not in the best possible way but at least it works. Although I was having problems with the following code:
This would give a result of catalogue.php&Genus=3?Page=2 for example. It always put whatever I was trying to add before the Page number and the question mark so this wouldn't work.
$self = $_SERVER['PHP_SELF'];
However I found that doing this later on with a line like this works fine and puts the code in the right order
So I've just used the GET clauses later on and maybe repeated a bit of information but at least it works!!
$prev = " <a href=\"" . $self . "?Genus=" . $_GET['Genus'] . "&page=$page\">[Prev]</a> ";
Thanks for your help!