Hi Bart,
By default, you are required to declare your world-wide income using the arising basis.
This means that you need to declare your foreign property income and claim a Foreign Tax Credit of up to 100% of the foreign tax paid.
The alternative is you claim the remittance basis and only declare your UK income and any remitted income.
Have a look at section 9 of RDR1:
Guidance note for residence, domicile and the remittance basis: RDR1.
Whichever option you chosse, both options are declared on a Self Assessment tax return.
Thank you.