You should not put the addhandler directives in /etc/apache2/conf.d/php5.conf, this disables the ability to configure php in ISPConfig. Also uncommenting the mime types will stop ISPConfig from configuring PHP. Just check the Vhost_ispconfig.conf file if php is enabled in the vhost.
Is there maybe a second www.fphosting.co.uk vhost somewhere in your Apache configuration that interferes with this one? Any errors in Apache's error log?
I just found the following error in the apache log: Code: an unkown filter was not added php I will try reinstalling php
This is just a warning, not a error and it does not affect the execution of PHP scripts at all. Are you sure that you access the website by its domain and not IP, is the Vhost_ispconfig.conf file included in your apache configuration file? Is mod_php loaded or do you use SuPHP?