I would check the aerial cable connections to the TV to make sure that they are in good condition and not loose. Also if you can, use the signal strength diagnostic feature usually found in the menu of a digital tv to check the signal strength and quality level of your TV channels signal. If the signal is of lower strength or quality it is more prone to interference than a stronger signal. It may be that there is a problem with your antenna cable or perhaps there is a something new between the transmission tower and your aerial that is partially blocking the signal reducing your received level.
If you have a second TV check the signal level that it is receiving and if it also prone to the interference from the ignitors.