Hi Jo,
So Sorry, an oversight on our part I'm afraid. It looks like Helvetica is not a free font for download. We already had it on our system and as it's very popular we incorrectly assumed it was installed by default on most machines.
If you don't have Helvetica, the closest alternative quickly is likely to be Arial or there are a range of similar fonts here;
www.fontspace.com/category/helvetica
We are going to re-develop this kit and change the font to a free to download alternative.
We are really sorry about this. We actually use Mac computers where it is installed by default and used it by mistake.
Hands up it is our mistake and we will try to rectify this as soon as possible.