Thank you for your inquiry.
if a user buys membership 1 for £100 (one off fee) which gives access to page one and after a week they want to upgrade to membership 2 which gives access to page 1 & 2 which is £200 (one off fee) is the a function where its classed as a upgrade not a new purchase so the customer who is upgrading would only pay a upgrade fee of £100 – totaling the membership 2 price of £200, however a new customer would pay £200 for membership 2?
s2Member gives you (the site owner) the ability to accomplish this. It isn’t an automatic change, because s2Member allows you to sell membership for whatever price you want at any time. You can have two Buttons/Pro Forms that givie the same exact Membership Access, but have one set up at $5, and the other at $500.
What you’d do to accomplish this is use s2Member’s Shortcode Conditionals to decide when a User should be provided the lower price (i.e. when they’re upgrading). Here’s an example.
[s2If !is_user_logged_in() || current_user_is(subscriber)]
In this part, the User is either not a member, or is a Free Subscriber (Level 0). A User that is demoted from cancelling might be s2Member Level 0.
Here you would give access to registration either for Level 1 at $100, or Level 2 at $200.
[/s2If]
[s2If current_user_is(s2member_level1)]
Here the User is s2Member Level 1, so you can have them upgrade for $100 to s2Member Level 2.
[/s2If]
[s2If current_user_can(access_s2member_level2)]
This part will show up if a User is Level 2 or higher. You should just tell them that there's no need to upgrade.
[/s2If]
See: Knowledge Base » Simple Shortcode Conditionals
Let us know if you have any more questions. :-)