The main effect for UK investors who have invested in non-reporting funds, as opposed to reporting funds, is that on disposal of their interests they will be liable to tax on any gain arising as if it were income (that is, an offshore income gain, or ‘OIG’) instead of as a capital gain.
IFM12300 - Offshore Funds: introduction: non-reporting funds
There are certain exeptions to this. Further guidance can be found here:
IFM13400 - Offshore Funds: participants in offshore funds: the charge to tax on disposal of an interest in a non-reporting fund