I doubt that you'll get any interest for the period after liquidation if the cash ISA funds are still with Icesave but, if the amount was less than £50k, you should get all the rest. There is a time limit for paying out of 3 months but I am unsure how that will apply because the UK scheme will only look at the funds that are left after the Icelandic scheme has paid out, but you should get the money within 3 months of the UK compensation scheme being applied. You should certainly try to keep the money under an ISA wrapped but this will probably not happen automatically so you should be prepared to keep all correspondence and make a few phone calls when the time comes.
Most stocks and shares products are protected by different legislation. If the ISA provider goes bust, the stocks and shares, or at least their value, will still belong to you.