I have spoken to my webhost about this and I have recieved the following response on an email:
"set_time_limit() is not enabled on the server our engineers have advised this is because it would allow the script to run longer than the script timeout.
The only real option would be to use a Virtual or Dedicated server, in which you can make as many changes to PHP as you like."
I don't suppose you would like to comment on this?
:(