Just to update you guys...
I had phoned up PC World's customer service and told them that the Manager had refused to even look at my printer or offer a replacement - quoting the 28 days crap.
Customer Service said this was wrong and they should have looked at it. They phoned up the store and explained this to a guy called Chris. Phoned me back and told me everything was sorted and to go back to the store and see Chris.
Went into store today and asked for Chris. Told him who I was and that he should have been expecting me. Blank look from Chris. Explained to Chris that I came into the store last week blah, blah.... and that customer service had told me that he was aware that PC World needed to take a look at my printer.
Another blank look from Chris who then spouted off the "it's after 28 days so the best we can do is send off the printer to Cannon and that will take quite a while..."
"No - NO Chris! That ISN'T what Customer Service told me!"
Another blank look from Chris, with a touch of bemusement thrown in for good measure.
Decided to phone up customer service. Quoted reference number to a very nice guy called John, who quickly got up to speed with the case so far. Handed phone to Chris.
After a couple of minutes of him nodding and mumbling, he sheepishly takes printer off to backroom to have a look at it.
Comes back after a few minutes and announces that the problem is that the printer isn't recognising the non Cannon ink cartridges. If I install Cannon's ink cartridges then all should be well.
So, I go and buy 40 quids worth of ink and ask him to check everything is ok.
Chris goes back with the ink and fumbles with printer for a few minutes.
Comes back out and announces that the problem is in fact that the yellow ink chip in the printer is faulty.
Goes over to the printer section and gives me a brand spanking new printer, including the ink.
"What about the ink that I just bought?" I ask.
"Er, um, well you can take that as well or get a refund on it".
"I'll take the refund, ta very much!"
Just proves that if you stand your ground with these guys and contact Customer Service you CAN get a result if the Law is on your side!