You got it through Argos because Mikomi is an Argos Own Brand and so only available through Argos.
Take it back for a refund. Under the Sale of Goods Acts, during the first six months Argos have to prove that is isn't fault rather than you prove that it is. Don't accept a repair, get your money back as you are entitled.
Don't worry too much about receipts. As it is a Mikomi it It must have come from Argos and the Argos shop will have a record of your purchase because they have to record and report the sale of TV sets by law.
T, January 2009