You will need to review the guidance at RDR3, to determine your residency status and whether split year treatment applies.
If it does, you need to claim it in a Self Assessment Tax return.
Residence, domicile and the remittance basis: RDR1
Yes, you will need to register for Self Assessment.
Foreign income is one of the criteria for completing a Self Assessment Tax return.
As your self- employment turnover is below £1000.00, you do not need to declare on a tax return.
You will need to declare the Capital Gain Tax, even although it may be covered by the annual exempt allowance.
Being a director of a company is not Self Assessment criteria.
You may find that it is just this one tax year, that a tax return will be required.
You can register for Self Assessment here:
Register for Self Assessment