I also bought my first computer from Dixons (same group) about 5 years ago and there was no mention of a refund in vouchers or anything like that. I have upgraded my computer twice since then and I have not and will not buy any warranty again.
reddwarfcrew, the voucher should be sent automatically at the end of the 5 year period, to whatever address you gave at the point of sale. It does happen, I have dealt with voucher offers. It started just over 5 years ago.
There is no hidden get out clause or anything like that, Head Office should send one automatically. If you don't hear from them within a month of expiry get in touch with Coverplan.
The current offer consists of: if you don't have a claim you get 20% off vouchers that can be used against price of PC and five year cover, or 10% if you have claimed. It may have been different back then.
To the first post I did the exact same thing. Just think of all the SAPS just like us 5 years ago who got the cover. 265 quid and not even a kick in the balls to go with it. Just think of the women we could have bought with the money. Doh!