If you get your advance in April, your next accommodation advance will be October 26th along with your salary. You need to be aware that if you opt out say on the 15th April, they will not advance you the full 6 months, they will give you 5 months plus 16th - 30 April, so you will in effect have 5.5 months advance. The following payment in October will be the full 6 months.
You will have to speak to your landlord and let them know you get paid on the 26th, my landlord was fine with this even though my rent is due on the 11th. This is a common occurrence and from what i have heard most landlords are fine with it.