Buy one of
these from Argos for a tenner
(I use one and can vouch for their excellence - mind you I have quite a few more appliances than you)
Then, have one SCART from your DVD player going into the scart box from Argos
One SCART from your NTL box to your VCR
One SCART from your NTL box to your scart box from Argos
One SCART lead from your scart box to the back of your TV
You then press the switch to indicate which source (eg DVD or NTL) you want to watch - prevents interference between the boxes.
You won't need a hook up from your VCR to the TV (although you can if you want), as when you press PLA on your VCR it will override the NTL box
Hope that helps.