Just in case you didn't know, you are allowed to earn £1k/pa interest, tax free, so unless you are going to earn more than £1k interest there is no need to bother with an ISA. You may get a better rate of return in a fixed rate savings account.
The income generated by either a cash or a stock ISA is not taxable. Any capital gain generated by a stock ISA is not subject to capital gains tax, whilst the original investor is alive. On death both types of ISA lose their tax free wrapping.