To confirm and hopefully add to what has been written above..
Your video records completely independantly of your TV; it cannot record what is on the screen. Instead, it uses its own tuner to receive a signal and it is that that it records. This tuner is analogue so when digital is the only option the tuner will no longer work.
None of this will affect the playback of previously recorded tapes as long as you are able to connect the VCR to the TV.
This also means you'll have to adapt the way you record using the VCR. You'll have to tell the VCR to use the input coming from either your freeview box or your Virgin box - how you do this will depend on the VCR but should be possible. The best way to check you've got this right is to tune the TV to show the picture coming from the VCR (as in when a tape isn't playing) then change the channels on the Virgin/Freeview box. If the picture on screen changes then the VCR is picking up this input, not the one from its tuner.
The next thing to be aware of is that if you set to record by timer you do not tell the VCR which channel to tune to (BBC1, ITV etc), you tell it to tune to the Virgin/Freeview box (as above). You then have to make sure that the Virgin/Freeview box is tuned to the right channel. (I find the autotune on the Virgin box useful, although slightly imperfect).
Set the timer on the VCR as normal.
Obviously, if you only have one Virgin box you can't watch one channel and record another, although I understand Virgin have a version of the Sky+ box that will allow you to do something like this; it might be worth investigating if you're thinking of upgrading.
See here
http://allyours.virginmedia.com/html/dtv/vplus/index.html
I hope this helps.