Excellent, help desk contacted me within a few hours and said new copies of the game don't have a limit on downloads, so they cancelled my old version and gave a code to get a new copy. All fixed now.
Was very good service, took a few days, but I think that was more a time-zone problem slowing things down than anything else. When I send an email at 9.30 am here, it is 4.30am in the US.
I'm going to put in another ticket just to let them know the email on the website is out of date, I suspect I may not be the only one who has tried to contact them on it.