UKradya, you are already UK resident and so the UK tax analysis of swapping a holding in a non reporting fund to a similar reporting fund should take account of the following.
The details of the UK tax rules on offshore funds is set out in a statutory instrument, Offshore Funds (Tax) Regulations 2009.
Reg 4 makes it clear that you need to separately consider each class of interests in a fund.
There is a general capital gains exemption, within TCGA 1992 s127, for what might be termed “paper for paper” swap of interests. Reg 37 disapplies this exemption. Instead a swap of interests will be treated as a disposal of the original holding at market value and an acquisition of the new holding at that value.
The above means that the course of action that you might be considering could trigger a charge to UK income tax under the OIG rules.
It is not relevant for these purposes that your original acquisition was made during a period when you were not resident in the UK. Further the original acquisition cost is used for this purpose (as calculated in sterling); there is no rebasing to market value on becoming a UK resident.