These are the risks of booking separate tickets. Prior to 14 days, all you are owed is a rebooking or a refund and you certainly have that. As the next day's flights are cheaper, if you take that option, request a refund of your current tickets and purchase the new tickets. If you elect not to overnight, take the refund and purchase the new OA tickets.

While unlikely, it is worth carefully reviewing your travel insurance policy to determine whether its travel interruption provisions cover this situation across tickets. There is a slight chance, so worth the effort.