Thanks folks...
I'm back in Texas at the moment, but aging parts willing, I'll be twixt here and New Orleans for the next while.
I've calmed down a bit now, and have fitted a cartridge to a HP Laser 4 Plus that has been doing nowt for many years. This gets me back in business.
I asked the nice manager from Staples here, if there was a head cleaner cartridge, he did not know of one, so I'll search on the suggested threads.
I have even sucked up the nozzles with a skinny plastic pipe to see if the dry ink was upstream of the head holes. All to no avail. I guess I may have wrecked the heads by doing this, but it stopped me hurling the thing into the river!!!
Anyway, thanks again. I'll try to get the solvent bottles. LR