Thanks to all for the comments.
Today, I went back and returned the toner cartridge to Cartridge World (I wasn’t going to mention them, but I feel the group needs to know who should be avoided). I ‘phoned them this morning to tell them to keep hold of the old cartridge as it had 2% left in it, which should suffice until I get the new HP-branded cart (points taken SD).
When I rang, the person who answered the ‘phone sounded as if he wanted a fight… After a string of insults (great way to treat a customer, my guess is he’s used to it) he said I could get a refund and hung up the ‘phone… I felt tempted to go in with a friend in case he was as pugnacious in person…
When I got there, the woman at the desk refunded me no quibbles.
However, I’ve now reinstalled the old cartridge to run a couple of pages off and they both have black streaks across them, as if something has leaked???
I will be ordering the legit HP item on Monday, but it would be appreciated if anyone has any suggestions regarding preparation before I put in the new cart so these random streaks can be avoided.
Many thanks again for the generous help