'X' months access until fixed date, then 12 months access thereafter

I have just purchased s2Member Pro. Membership has to run from 1st April for 12 months. I wish to use the below scenario:

  • Membership starts from 1st April and is £120 for 1 year.

  • When someone signs up, they will pay the number of months until this date (ie 12 February signup will sign up for 2 months and pay £20). 7 Days before the 1st April, they will receive an email reminder to pay the £120 (I do not want this to be automatically taken). In 12 months time, they will receive another reminder to pay the next 12 months (7 days before).

  • I understand that I will need to manually ammend the form shortcode each month to a set price, this is not a problem.

Thank you