s2Member-Pro-PayPal-Form inside an iframe but then issues with Paypal?

I have an s2Member-Pro-PayPal-Form which is inside an iframe. Submitting the form causes Paypal to load within the same iframe.

Is there any way to change the S2Member source code to load Paypal to load in its parent frame or in the top.location of the page ?

Any assistance with this would be a great help.

The short answer is no. iFrames are protected in browsers from accessing their parents for security reasons.

If you are trying to sell subsites on a multisite installation then look at the following plugin https://github.com/wpmudev/pro-sites