Hi Simon
I’m not using Helio, I’m using Telline II, but had the same problem. I wanted to gather more information!
In the end, I installed a commercial 3rd party extension on my site which solved my problems: extra data on registration, captcha security on input forms, statistics, etc.
The extension was easy to install and configure and well worth a look, plus the tech-support is very good, to the extend of Skype calls or even mobile telephone numbers!
http://joomsuite.com/index.php?option=com_resource&view=article&article=17&Itemid=13
Cost me 19 euros, but money well invested. Sorted out all my registration and user issues.
Hope this helps
Chris