Regrettably, this is a known issue with FileMaker 12.
For More Information see: Filemaker 12 Slow Printing
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip
Thanks Phil, shame the issue still hasn't been resolved but that's a great idea what you've done with the "Known Bugs List".
Thanks for your help.