I've contact support at the company - through Twitter, and also through their ticket system, but not heard back yet. And that has made me wonder whether we should look for another company to build and host the app.
http://isites.us seem to offer a similar service too, and offer the ability to make changes to the app without additional cost. Looking through their options I noticed that they do display ads on the finished app. For a school based app this is an issue for me - not having control over what is displayed on an app that children will be using is worrying, although reading their FAQs section I saw that they offer an ad-free version for $100 a year.
So, now I have a decision to make - stick with the current app maker company, and hope that they sort out the quitting issue and then everything is fine, or go with the alternative company, and pay a yearly fee to keep adverts off the app.
Decisions, decisions...

