Hi,
You can hold foreign stocks and shares in a share ISA, as long as they are listed on a recognised stock exchange.
There is a list of investments that ISAs may purchase at:
Stocks and Shares investments for ISA managers.
Capital gains tax arising from the disposal of foreign assets, woud be payable in the tax year that the gain arises, even if you do not remit the gain to the UK, as income tax and capital gains tax are charged on the 'arising' basis.
Thank you.