By reducing cash ISA limits to push stocks and share ISA's, government will take more in tax than from traditional interest. 20k means multiple stamp duty payments of £100 if stocks are traded. If the government are serious about people investing to better their savings, scrap stamp duty in an ISA.
It is an absolute disgrace that government is penalising savers by increasing tax to 22% on interest whilst reducing cash limits in ISA's and pushing people into stock market investing where the government takes 0.5% of every £ invested regardless, of that being in an ISA / SIPP or regular account, and regardless of whether the investment makes a profit or loss. Stamp duty is a tax and as no place in an ISA wrapper.