As per the title.

We have an LG television in the bedroom on freeview, picture quality off the aerial is good, we also have a dvd player connected via scart and we have found that if the aereial is disconnected from the TV then the dvd picture is fine.

The problem occurs if the aerial is connected then the DVD picture has interference on it (difficult to describe, but like diagonal fringing drifting across the screen.

Tried different scart leads but no change. The dvd player has no HDMI output or I would have tried that, it does have Composite video & S-Video outputs. The TV has HDMI, Scart, RGB, DVI-D and component connectors, which would be the best option to eliminate the problem please?

Have you tried a fully screened good quality scart lead?

It sounds like crosstalk from the tv sending it's freeview picture out of the scart socket interfering with the video from the dvd coming in.

Sounds like it could be video breakthrough.
Causes and solutions here http://www.satcure.co.uk/tech/scarts2.htm#vb
From the above "You can safely disconnect pin 19 (at the TV end) for any equipment that is sending its video TO the TV set and not expecting to receive a video signal back"

I concur, it's a very poor quality SCART allowing crosstalk from the TV output to the input of the SCART cable.

Thanks for the suggestions, I will try a better quality Scart lead.

Any advice about how much I should look at paying and the best place to buy?

P.s. Tried disconnecting pin 19 as suggested above but no difference unfortunately.

If you are still getting interference with pin 19 disconnected then either you've disconnected the wrong pin (or the wrong end of the cable) or the crosstalk is not being caused by the cable.

If you set the TV on the SCART input and unplug the SCART lead from the back of the telly what happens? Apart that is from the DVD picture vanishing of course. If you can see something on screen then it is possible the interference is being generated in the TV.

Also have a look in the menu system of the TV. See if there is an option to change what is being sent back down the SCART lead. It is possible that it can be switched between Tuner and maybe a second SCART input. If you do have that option try setting it to whatever alternative there is to the tuner and see if that helps.

As for SCART lead. Any that says it is "Fully Screened" should be OK. It is unnecessary to spend a fortune on a cable. The likes of Currys will rip you off by pointing you at a cable that you pay 50 quid for but they pay only 5 quid for!

As you have opened the scart plug it is easy to see the quality. You need a lead where nearly every wire is a mini coax with its own screen. If all 21 wires are bunched together with only one screen around them the lead is no good.

Assuming the OP opened the plug. The other common option is to break off the pin in the plug!