Many thanks for following up Waterboy.
The suggested method made no difference whatsoever. The instructions' final solutuion is to replace the print head. This I ahve done (to great expense) and still no joy. The printer now tells me my ink cartidges (HP originals with hardly any use) are leaking and refuses to do anything. They patently are not leaking. Really, really frustrating. The machine's abilities are fantastic but the technology under the hood is clearly lacking coherency and relaiability. Will probably now replace with a different brand...