I thought this would come in useful to some. Argos don't seem to be part of any cashback sites but until the 21st March, if you've got a nectar card you can earn 2 points for every £1 you spend. Simply do your transaction through nectar e-stores. Could collect quite a few points on a large purchase and offset that £4.95 delivery charge.
Strange - the link kkeps going to argos home page.
Link is :http://www.nectar.com/dynamic/estores/nectar/home