You can only use the suppliers listed on
this page. These are approved by HMRC to accept electronic files - although the one you've found is on there. You have to purchase the software each year you make a submission.
But you also have to have all the self-assessment codes etc set up by registering to file online. Luckily I was in the system from when I did self-assessments a few years back.
The tax return software normally costs around 15-20 quid a year.
I've used Andica and Ftax (although the latter no longer appears on the list). Not all of them are for individuals.