Hi Dave,
I bought a Sharp 15inch LCD TV last year, after a bit of looking around shops and looking at the back of the sets on display I noticed very few run on 240v ac. Most use a small transformer and a plug similar to a mobile phone charger to supply the TV with a dc voltage, different makers use various dc voltages, the Sharp I found was 12volt, I think this is now obsolete but the newer models may also be 12volt, you would have to check on the back of yours or the display models in shops, the voltage is normally moulded into the casing around the input socket. I got a plug from Maplins and used a standard caravan 12volt plug to make up a lead, I dont use the transformer at all now even when on mains as the 12volt lead is fine, I also got a freeview box [Sagem] which is 12volt and this works well when a good signal is available. The lead is easy to make if you have a soldering iron. I hope this helps
Simon.