Do I qualify for tax exemption in Portugal?

Hello,

I have started working just over half the time for my UK employer at home in Portugal. My employer did an assessment and determined that in these circumstances I would still pay UK PAYE (which is clear from the tax treaty between the two countries) and I am still paying national insurance in the UK. So, so far, no change.

I am intending to register as a non-habitual resident. My question is about the tax exemption:

"3.1 Income derived from employment (category A) is exempt from any taxation in Portugal if:

a) It is taxed in the country from which it derives, according to the double taxation agreement in force between that country and Portugal or, in the lack thereof, according to the OECD Model Tax Convention."

and whether it applies. It seems to because the income is taxable (and will have been taxed) in the UK under the tax treaty. Anyway, has anyone seen this situation before and, if so, can confirm (or otherwise!) that I will have no additional tax liability in Portugal?

Same question for national insurance / social security.

Thanks in advance for any help,

John