Virgin states in their customer updates that “Beginning on August 16, 2010, the charges for pay-per-use web browsing are changing from 5¢/page viewed to 10¢/page viewed. If you don’t use your phone’s web browsing features or have already hooked up to one of our Data Plans or Unlimited Mobile Web Browsing Add-ons, then this pricing change won’t affect you.”
So you’ve got about a months notice to change your plan over before being charged double for every page you view.
UPDATE: Virgin has revised their website and pushed back the date for this to increase to August 20th.
Check it here at Virgin