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Do not take that option. It will either mean you are billed , or if not within a few days you will receive an email from Netflix saying account is cancelled as Virgin will not pay.
You need to wait for the email with the correct activation link that says Netflix is included in your bundle.
I have been waiting nearly 3 months for that email now - they are still working on it !
They should not have been offering it as an option for all this time whilst they were very aware they had a problem supplying the product.