So it looks like this is it. I will submit my project tomorrow.
With your help i have now 3 different shops with one admin application working together.
They share membership and now they even can use one login across all applications.
This article : http://msdn2.microsoft.com/en-us/library/eb0zx8fc.aspx
is very helpful.
Thanks for your patience and help. I really mean it.
All the best mate.