Non-resident pages for self-assessment tax returns

I am currently overseas on secondment and trying to complete my tax return obligations in the UK for a year in which we were non-resident for the whole tax year.  We have small amounts of interest and rental income (but overall a loss) which I have included in the return.  However, I'm struggling on HMRC's self assessment system to understand how I show my non-resident status.  I believe its the SA109 form but am I correct in understanding that its not possible to use this form in their system and therefore you can't submit your return without a tax agent or access to commercial software?  To force you to use an agent just to get a simple tick box form into your return seems at odds with simplification and helping people to do their own returns.  Can anybody tell me whether I can submit the form myself or do I have no choice but to pay someone just to get this form?  Thanks