1) if you're using an s-video cable, you also need to connect an audio cable (most likely red&white connectors). There's no reason why that shouldn't work and allow you to watch the DVR on "AV/SVHS" input.
You may have to fiddle with the settings in your TV menu to set up the AV/SVHS input correctly.
2) if you want to record analogue while watching digital, this should work:
- connect DVR to AV/SVHS as above
- connect NTL cable (co-ax) to NTL box, take TV out co-ax from NTL and connect this to the DVR "RF in" or similar
- connect "RF out" from DVR to "RF in" on TV (normal aerial connection).
- you will then have 2 scarts from the NTL box, one going to the TV, and the other going to the DVR, and a S-video(plus audio) going to the TV from the DVR
- you'd also need to tune the analogue stations into the DVR, and use "Ext1" or similar on the DVR when recording digital.
- to watch analogue while recording digital, use the TV input on the LCD, although there might be a loss of quality with all the cabling going on.