Hi Skinny,
Yes.
Any foreign income not remitted to the UK, must be declared on SA109, on page RR3 in boxes 34, 35 and 40, which will require the completion of a self assessment tax return.
If you chose the remittance basis, then you lose your personal allowance / capital gains allowance and will be taxed on all your UK income and any remitted foreign income.
If you are resident in the UK for 7 of the last 9 years, a charge of £30000.00 applies.
If you are resident in the UK for 12 of the last 14 years, a charge of £60000.00 applies.
These charges will be added to your taxable income and tax charged on the total.
Have a look at the guidance at section 9 of RDR1
Guidance note for residence, domicile and the remittance basis: RDR1.
Thank you.