All of the computers are on DHCP allocation from the router. The scope is ample (100 addresses for a network of 6 devices). All the settings on all the computers re TCP/IP, networking etc (bridging was not necessary on any of the computers) are identical. All were running firewalls which were disabled for the setup process.
As I say, it's cured now by using that reluctant laptop to configure the network for all the computers on the net. Not one setting has changed, that I can see! And, remember, there was no problem whatsoever until I moved the printer.
Computers! Can't live with them; can't kick 'em in the bolleaux!