Or if you've got a video recorder with a scart socket spare, you could plug this into your tv, with the normal ariel lead, then connect your DVD through the scart socket on your VCR.
Some older TV's have got AV sockets. If so you can buy a Scart to AV lead for �1.97 from Tesco Extra and use that. (Or, if your DVD player has AV outputs, you can just use ordinary AV leads). Otherwise, unless you add a VCR to the system (as suggested by John) you'll have to use an RF modulator (as suggested by Kempie).
if you've got no scart or rca inputs on your tv and only scart output on your dvd player, you need to buy a modulator. You can pick these up from your local tandy etc, they cost around �35 to �40 normally - might well be cheaper to buy a video like john says