Yes, you must have sufficient funds in your account to cover the full cost of the shares you are indicating an interest in acquiring, based on the maximum price in the offer price range (or such other price as may be specified in the offer documentation). When you submit your indication of interest, these funds will be set aside in your account. You will not be able to use them for other purposes until the allocation process is complete. Please allow for an extra buffer in the account to cover any foreign exchange, should the price be in a currency which is not the currency of your account.
If the IPO does not proceed or you do not receive an allocation (or receive a reduced allocation), any funds that are not applied towards the purchase of shares will be released back to your account, in accordance with the timescales set out in the offer documentation.
You should therefore ensure that you are comfortable with not having access to the relevant funds for the duration of the offer period.