Hi
I needed to do this last year, and like you had some problems. What you need to do is get the Disney confirmation number from Virgin, it took me several attempts to do this, I ended up going through to the Frequent Virgin Club option when phoning Virgin and they gave me the Disney Hotel confirmation number straight away.
You can then ring ME direct, quoting your reservation number. I don't have the telephone number to hand, but I found it on the WDW web-site. If you have problems getting the number, send me a PM and I will go through my paperwork to try and find it for you.
Hope this Helps