Yes, I have cleaned it using the relevant printer utilities.
I will do as you suggest later on. I shall be busy this afternoon on other things but will reply when I can - probably tomorrow. Thank you for your help so far.
I have cleaned the printer manually as you suggested with the result that the faint horizontal white lines between the thicker white lines seem to
have disappeared - certainly an improvement !
Have you any suggestions as to how to get rid of the remaining white lines, please ?
Although I have done as you suggested and have cleaned the printer again twice, I'm afraid the thicker white lines are still present. Is there anything else that can be done, please?