Thanks for the circuit. I gave it a go but got the same results, a distorted picture.
But it's all good now as I've just found another circuit that will limit DC down to 0.2 to 0.6 volts which I guess is pretty acceptable for DVD recorders, I put it together and it works very well. The circuit can be found here
http://www.telestream.net/pdfs/app-n..._DC_Offset.pdf . I had to add a 75 ohm resistor in parallel from video signal to ground to make the circuit work effectively to limit DC.
I am using this for the viewfinder output from my JVC GC-3300E colour camera
http://www.troysvintagevideo.741.com/gc3300.html as the viewfinder is not working and I want to use a little Casio handheld TV in place as the viewfinder. That circuit has effectively limited the DC from over 3 volts to about 0.6 volts which I guess should be okay for the AV in of a small handheld TV.