Thanks AMDbuilder for your time looking at this.
I've finally got somewhere with this.
It was to do with the issue mentioned here:
http://stackoverflow.com/questions/5165183/apache-permissions-php-file-create-mkdir-fail
I then spoke to the host who said enabling FastCGI should help, the guide here was useful for plesk control panel:
http://kb.mediatemple.net/questions/1890/(dv)+How+do+I+enable+FastCGI%3F#dv_40
I then encountered another problem as could no longer view the setup page, was getting a session path error. Again the hosts helped me out. This time they needed the system admin team to do something behind the scenes. I was told they create a symlink between the tmp and the current set session path folder. This solved that issue and so far so good with my revo instal.
The hosts in question were Heart Internet, thought i should mention their name as they particularly helpful.
Oh and control panel installed is plesk, which from googling might of been part of the problem with the session path.
Thanks
Ben