Can I not pay the insurance excess that I received?
Why wouldn't you pay the insurance excess?
Because my insurance is going to pay anyway.
You should pay for what you owe on your insurance. If not, you might be responsible for the charges later and damage your finances.
I know it's my fault, but they are going to pay the excess anyway.
If you are not sure the insurance is going to pay the excess, then you should pay what you owe. It's only fair to do that since you have used the insurance.