The UK tax on self-employed earnings of £260,000 for 2012/13 will be £108,126.00 and the Class 4 National Insurance Contributions will be £7,488.50 so your total gross liability will be £115,614.80. As you have paid tax in Azerbaijan of £74,000.00, your net UK tax and NIC liability is £41,614.80. This will be payable on 31 January 2014.
If you are still self-employed, your will have to make payments on account of your tax and NIC liability for 2013/14 of £20,807.40 on each of 31 January 2014 and 31 July 2014. That's assuming you will continue to pay tax in Azerbaijan. You can apply to reduce your payments on account if your 2013/14 earnings are less than those for 2012/13.
If you incur expenses, you may be able to claim these against your earnings which will reduce your tax and NIC liability. You might ask your colleagues what they do in this regard.
Your self-employed earnings are covered by Article 14 of the UK/Azerbaijan tax treaty here
. Article 22 allows you to offset tax paid in Azerbaijan against your UK tax liability.
I hope this helps but let me know if you have any further questions.