The retailer (in this case Ideal Shopping Direct) is responsible for remedying any problem that occurs due to an 'inherent fault' (i.e. poor quality components or poor manufacturing standards) for 6 years after purchase.
During the first 6 months there's an automatic assumption (unless there's clear evidence to the contrary) that any malfunction is due to an inherent fault. Thereafter it's up to the purchaser to show, based upon the balance of probabilities, that the most likely cause of the malfunction is an inherent fault.
The retailer is obliged to either repair or replace the faulty item. The purchaser can indicate which of these options he'd prefer but the retailer can substitute the alternative option if the first option is uneconomic. (The purchaser has no right to a refund after he's initially 'accepted' the goods. Since your digibox worked OK when you first got it, you've legally 'accepted' it).
Contact details for Ideal Shopping Direct (who trade as Ideal World) can be found here:
http://www.idealshoppingdirect.tv/contactusF.a sp
Chris