Hi.Assuming you are UK domiciled, ie a UK national, you are taxable on your income and gains from wherever in the world they are derived and regardless of whether the income or gains are brought into the UK. There are different rules for non-UK nationals living in the UK who have non-UK source income.
According to Article 13 of the UK/Mauritius double tax treaty, gains from the disposal of what the tax treaties refer to as "immovable property", a term which can include homes may be taxed in the country in which the property is situated. That means any gain you make may be taxed in Mauritius. Article 6 defines immovable property.
If you do make a gain when you sell the property, it will be taxable in the UK but you will get credit for any tax paid in Mauritius on the same gain under Article 24 of the tax treaty against your UK CGT liability.
You can find more details on the meaning of the clauses in most tax treaties here. Immovable property is more clearly defined here.
I hope this helps. Let me know if you have any further questions.
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