The “excess period” is chosen by you and is the length of time that you will have to wait before you can make a payment protection claim. Your choice will determine when the monthly benefit can be paid/received under the terms of the policy. Whatever period you select you cannot make a claim unless you have been unable to work for at least 30 consecutive days.
The “initial exclusion period” is something that applies to all payment protection policies regardless of the provider. However it only applies at the start of the contract to unemployment claims and it states the period during which no claim can be made. See What Is The “Payment Protection Initial Exclusion Period”.