I know what you're talking about - I tried it! Apparently you only get to see the actual amount discounted once you have completed the transaction, i.e. they don't reveal the mystery on a dummy booking. I tried tons of them before I booked. I booked over the phone eventually (after hearing conflicting feedback about the reliability of the website) and was told that you do indeed get a discount online but the percentage can vary and no-one seemed too clear on what it was. I did do a flight inclusive booking though so I can't speak to whether a discount applied to a room only. I did notice however, that when I did my quote online, Disney charged my child at a child's rate plus single supplement - and that was the pre-discount rate, so at that point of the booking process, they were still promising the magical discount on completion of the transaction. (I am a single parent with one young child - not the cheapest way to travel anywhere!) But when I did my actual booking and (finally) received the written confirmation, I paid full adult price for my seven year old, which worked out, across the whole package, several hundred pounds more than it would have been if I had done the booking online. I don't let it bother me too much as this is the way it's always been, but I may take a chance the next time and see if it does work out any cheaper doing the online thing. I would guess that Disney offers a similar discount to the Virgin website, but I couldn't tell you for sure.
When Virgin does the discount online it is 10%, but they first deduct the cost of the park tickets, taxes/fuel duty and Dining Plan (if applicable), so effectively the discount is on your accommodation and flights.
