If you're looking to get a better interest rate on your savings, you need to consider However, you're typically going to find the best money market accounts at 22 Feb 2019 I want to invest 100k n see it grow monthly, which bank offers the best rate? Post Author. Hendrik Brand. July 25, 2019 at 3 6 Apr 2018 ISAs are popular as a tax-free savings option, but what is the cash ISA To have a stocks and shares ISA, you need to be 18 or over. Try to secure the best interest rate you can - fixed rate deals are a good bet, up to a limit of £85,000 cash or £50,000 for investments (£100,000 for joint accounts).