OK, this has got me thinking again. I was blindfolded into thinking it was something wrong with the PayPal Subscription and never thought about the roles and caching / cookies.
By doing a simple test, of altering a users roles manually, I see that the roles caching/ cookies is the problem.
Now to try and solve it, using your advise to look at web.config, I changed the cacheRolesInCookie from true to false.
<roleManager cacheRolesInCookie="false" cookieName=".ASPXROLES" cookieTimeout="30" cookiePath="/" cookieRequireSSL="false" cookieSlidingExpiration="true" createPersistentCookie="false" cookieProtection="All">
Unfortunately, it didn't work straight off, I am now waiting 30 minutes to see if expiration of any existing cookies might be a problem.
One step further, but not there yet.