Yes, you can add more money to your fixed rate bond if the product is still open for funding, up to the maximum deposit amount.
If your bond is removed from sale (we'll do this when we have new rates), you'll usually have seven days from removal to add any more funds to your account.
You can check if a product is withdrawn by checking the savings documentation page and checking the withdrawn product list.
You're welcome to take out an additional bond if you wish for further funds.
Just log in and send a secure message to apply for a second account.