My printer is working again! Hallelujah! :)
After a day of frustration spent searching online for deals on new printers, and then for specialist cleaning cartridges that were compatible with my printer and then attempting, as a last ditch effort, to put the cheap ink cartridges back into the printer and run multiple cleaning cycles, only to find that the stupid printer wouldn't acknowledge that the cyan cartridge was present when it was.... I finally got the darn thing to accept that all the ink cartridges were present and I started running cleaning cycles.
Bearing in mind that I had run probably 10 cleaning cycles only a day or two before with absolutely no change in the amount of yellow ink that was getting through.... this time, after the second cleaning cycle, suddenly a lot more yellow was getting through! So I ran a couple more cycles, just to be on the safe side, and the test print was showing all colours printing normally so I printed a nice complex colour design from my Joanna Sheen CD to try it out... and lo and behold, it's printing colours normally again!
Hurrah! Print head unblocked, problem solved, no need to spend £80+ on a new printer!
So I can actually print some photos now and get some scrapping done!
All I need is the time... oops. :D