My dad fell foul of this, he didn't notice there was a "non returnable deposit" phrase on his order form so he lost £100 when he cancelled his order. I offered to take him to the shop and take our money back in plate glass
but he declined.
I'd phone them and explain that you've changed your mind just out of courtesy and leave it like that, I'm certain you won't be the first person to examine your finances in this day and age and decide to play it safe!