If when trying to create your MWS keys you get an error on Amazon:
"Sorry, you do not have sufficient rights to view this page. Please contact your site admin if you think you have received this message in error."
it means you need to upgrade your Amazon seller subscription from an individual seller account to a Professional seller account.
Here's the links to do that:
UK: https://services.amazon.co.uk/services/sell-online/how-it-works-pro.html