This is along the lines of a hypothetical logistics question, and the answer is probably obvious. If the British didn't gain the capabilities to break the Nazi military codes, would it have made the Allied victory that much longer and more difficult, if at all?
The biggest difference would have been at Normandy, where the allies would not have not known how well their deception plans worked, Alamein, where Rommel may have been able to achieve surprise and Kursk where the Soviets would not have been able to plan so well for the German attack.
i would have to disagree with the kursk thought as the russians had far more reliable spies inside the german high command.