Tax for Non-resident Landlord

Tax Planning and Financial

Hello,

In case I leave the UK I need to have a property agent looking after my properties. One prospective agent has sent me the following:

"If you're living outside of the UK for 6 months or more HMRC will consider you a non resident landlord and there is a form that you'll need to fill in (NRL1) so that your rent isn't subject to tax at source. Once HMRC has processed this you can receive the full rent without this tax deduction (although you would still be liable to pay tax on the profit at the end of the tax year for profit made from your property during that tax year via a self assessment tax return)"

I am puzzled because I don't pay tax at source, I pay once a year via self-assessment. Should I be doing this? 

When I leave, I think I would stay resident for tax purpose and keep 2 rooms in Lynton Gardens for contact with my son (in a UK University) and having a place to stay when I take my young daughter to visit her dad in Harrogate. I don't foresee having French income as I would be looking after my dad but inheritance is a possibility for medium term future. 

I have browsed RLA docs and they seams to be out of date (2015)

Any advice on tax planning? Should I become a non resident or stay resident for tax purpose?
For info: I am a lower rate tax payer, I have no LTD.