To help you develop an idea of how your tax situation may evolve, we need to look at, at least, two scenarios. Two scenario, not only because your question is not detailed enough and assumptions must be made (hence, different outcomes) but mainly because you may have an opportunity to predetermine your tax position.
1) Tax residence in Cyprus
If you accumulate over 183 days of physical presence in Cyprus during a tax year (January - December) you will become Cyprus tax resident and as a result taxed on your worldwide income. If you receive any income from UK or Angola you will need to declare it in Cyprus through a self-assessment tax return. The tax returns are obligatory for all individuals who have taxable earnings of over €19,500.
Currently the personal income tax rate in Cyprus are:
0% from €0 up to €19,500
20% from €19,501 up to €28,000
25% from €28,001 up to €36,300
30% over and above €36,301
The above are progressive tax rates, in other words, the tax rates increase for and up to the corresponding amount only.
To illustrate for the sake of clarity, slice your taxable income, say €40,000 into the tax brackets as follows:
First €19,500 are tax-free 0%
The following tranch (€19,501 up to €28,000) = €8,499 @ 20%
The third tranch (€28,001 up to €36,000) = €8,299 @ 25%
And finally from €36,301 up to €40,000 that is €3,699 @ 30%
As far social security is concerned, if you are employed by an Angolan company, you need not worry about the 6.8% Cyprus social security. However, if you are employed by a Cyprus company and receive income from Cyprus, than there will be social security on the portion that relates to your employment in Cyprus. In any case, social security is a tax deductible expense and you get the comfort of having a state pension in the future.
Newcomers to Cyprus are given 20% exemption (with a max of €8,550) on their remuneration for a period of 3 years starting 1st January following the year when they started employment (Note: not when you come but when you start employment). Thats a good amount of allowance and if you ever become Cyprus tax-resident make sure to claim it.
2) Being a non-tax resident of Cyprus
Making less than 183 days Cyprus, on the other hand, makes you non-tax resident. You will be liable to 10% flat withholding tax but only on Cyprus source income. Any income from UK, Angola etc. will not be subject to Cyprus tax. Furthermore, you do not need to file tax returns in Cyprus.
When you relocate to Cyprus is also important. From a tax planning perspective, it is usually more favorable to come in the second half of the year, in order to avoid becoming tax resident in the year of arrival. However, this is not always the case and you should consider your individual circumstance. What should guide you is a comparative approach of what your tax liability is today with what will be if you become tax resident of Cyprus. Of coarse, it goes without saying, that you have the option of choosing whiter to come in March or April 2012 or July 2012.
As you see, the scenarios emphasize on the 183 days rule; however, this is not the only and the most crucial factor.
3) Key elements influencing your tax position
a) Timing your relocation to Cyprus
b) 183+ days in Cyprus or not
c) Signing a contract with Cyprus or Angolan company
b) Signing an employment contract or service agreement (i.e. employment through a service company)
4) Cyprus or Angola tax
On another note, what you need to consider is that personal income tax in Angola is much less than that in Cyprus, max. 17%, and social insurance is 3%. Furthermore, the most favorable element seems to be that Angolan's tax law does not deferential between tax and non-tax resident. Their government taxes everything that is paid from Angola-sources and nothing from outside sources (i.e. the concept of worldwide income is inexistent).
Finally, You may want to check one of our articles "Do I have to pay personal income tax?
" which talks about an even more awkward cross-border tax case.
Hopefully this was informative enough and has helped you sufficiently appreciate the sensitive areas.