Hi Helen,
Hope the kittens didn't get in to too much trouble :) I'd advise giving HP Support a call, as you'll require a replacement printer (the printhead in this model is non-removable). Are you based in the US? If so, check out the link below..
[URL|'''http://support.hp.com/us-en/document/c04839288''']
Click 'Contact Support' at the top of the page for further details. If there's anything I can help, please feel free to contact me on the HP Support Forum or Twitter.
[URL|'''http://h30434.www3.hp.com/t5/Ink-Toner-Cartridge-Printhead-Issues/bd-p/Ink''']
[URL|'''https://twitter.com/Ciara_B_HP''']
Thanks, Ciara