Just back from my local ASDA (Bishopbriggs - Glasgow) where I got 2 generic Canon cartridges to fit my Pixma MP150 for £8.
Individual cartridges for my specific printer were listed as £9.50 (black) and £13.50 (colour) approximately, checked against the Canon's own "40" and "41" branded cartridges also on sale and the ASDA ones were considerably cheaper and had double the ink. I saved over £15 on the combined list prices.
If I had bought the branded ones I wouldn't have got much change from £45
If I had bought branded cartridges to get the same amount of ink I would have spent £90
As it turns out I spent £8
Not sure if its store specific or national. I've only been able to find a picture of one type on the ASDA website, however its the same packaging with a different background colour behind the printer manufacturers name (purple in the case of Epson)
Maybe suggest calling your local store and asking for electrical/entertainment department via http://www.saynoto0870.com/
and typing in ASDA in the search function.
It won't work out as good a deal for everyone, my printer uses pretty expensive cartridges so I make quite a big saving. Hope its of use.