I buy mine from ebay, and have done for a few years now.
Even if my printer goes pop eventually from it, I'll just buy another printer and do the same thing.
The price for genuine inks is shocking, and given the price of the printers, you only need to buy 2 lots of refills and you could buy a new printer.
http://stores.ebay.co.uk/RW-INKS-AND-TONERS?_rdc=1 is where I get mine, something like 20 cartridges for £10, if I bought 20 genuine ones, it would be £180 roughly.