I have followed Jonathan's advice and acquired a ZD-1211b wireless USB dongle.  
And I have been crawling thorugh setting it up at the rate of an hour or 2 on 
the internet and one small step, followed by an hour or 2....
But although I have managed to progress a bit, crucially iwconfig still tells 
me (odd choice of name the box's, not mine):
eth1   IEEE 802.11b/g  ESSID:off/any Nickname:"zd1211"
          Mode:Managed  Frequency:2.412 GHz  Access Point: Invalid
The nickname was supplied automatically, so it has obviously found the right 
card.
And ifconfig gives me its hardware address, so it must be seeing it.
But I cannot get past that "Access Point:  Invalid", which Google suggests 
refers to the card being "off" and not to anything being wrong with the AP on 
the router.
Has anyone any ideas??
TIA
Lisi