I can wait a bit more, thank you.
My question is, with this arrangement, do I need to pay Tax and NI? If so, how much do I pay and how do I pay it? My own idea is that I should not pay tax as I'm doing the work outside of UK. But I'm not sure about NI. Could you please explain this matter to me?
As far as Income Tax goes you should complete a form P85 when you leave the country for Iran. This would enable the tax office to get your tax right.
More information on this and Form P85 be can found here
As far as national Insurance Contributions are concerned, you may wish to consider making voluntary contributions to ensure your entitlement to the basic State pension and certain bereavement benefits.
General information on National Insurance Contributions and whether you need to top up your NIC can be found here
More information on paying voluntary contributions for periods spent abroad can be found here
I hope this is helpful and answers your question.