Found it, it is described in:
http://shop.virginmedia.com/the-lega...gal-stuff.html
Talk 08 £2: Includes 250 minutes each month of direct dialled voice calls calls to UK numbers starting 0845 or 0870. You must keep your Talk 08 £2 package for at least 30 days. Available to Virgin Phone customers only. We reserve the right to vary the inclusive minutes within the Talk 08 £2 plan. We will publish these changes on our website, so check virginmedia.com/callingcosts regularly. The changes will take effect when posted on the website. Further terms and conditions apply, see virginmedia.com for details.
Talk 08 £5: Includes 250 minutes each month of direct dialled voice calls calls to UK numbers starting 08. You must keep your Talk 08 £5 package for at least 30 days. Available to Virgin Phone customers only. We reserve the right to vary the inclusive minutes within the Talk 08 £5 plan. We will publish these changes on our website, so check virginmedia.com/callingcosts regularly. The changes will take effect when posted on the website. Further terms and conditions apply, see virginmedia.com for details.
So it would appear a review-customer is a phone customer that stays on the Talk 08 for at least 30 days. Isn't this actually true for any VM phone customer?