You can't withdraw money. You can close the account early or transfer your money to another ISA but you would be charged. The charge will be the same as 180 day's worth of tax-free interest. This means you may get back less than you put in.
Any money you move to an account that isn't an ISA will lose its tax-free status. Tax treatment depends on your individual circumstances and may change in the future.
If you change your mind, you have 14 days from opening the account to cancel it. You will get your money back without being charged.
After the two year term ends, the account will change to an ISA Saver. Before this happens, we'll contact you to explain your options and next steps.