Thanks very much for the feedback draythomp- Ive only got UNOs sitting on my desktop at home which is why I haven't encountered any of the problems you guys are bringing up. I may update the tutorial at some stage or another but for now the forum thread is short enough for someone to be able to skim and make changes at a glance - great timer work-around! 
I presume you only added the Serial in the WDT interrupt to debug and get some sort of feedback - Ive never encountered any problems but just be aware if serial happened to be the function that caused the board to malfunction and prompt a WDT interrupt, It may cause the interrupt to hang if you bring up serial in the interrupt and you will never get around to resetting the board.
Thanks again for the feedback! Such contributions are what make forums such great mediums