Use the post type name label value rather than the post type name

When generating the title - you use the post type string passed as `$_GET` however this isn't always very user friendly - for example when registering a post type I often prefix the post types eg `matt_product`. 

It might be nicer to get the post type object, and then use the labels that you can specify when registering the post type.

Also - i've added some escaping on output.