I keep looking into getting some HP 21/22/58 cartridges for my F2280 printer. However, just when I think I've found a cheap supplier, I check for reviews, and they have an awful reputation (e.g. multiple cases of nothing received and no refund, reports of no real stock, etc). There's also the issue more...

First time i've had to buy ink for my HP Deskjet D2360 printer.
Black cartridge HP21, Colour HP22
Found the black on inkstore.co.uk £8.75 + free P&P

Sorry, is this a good deal? I'm just not sure how much I should be paying?
Thanks to anyone with info on this.