Thanks guys for all the suggestions and comments. I have it sorted now. I got some tech support from Scorpion Tech whom I bought the IP power.
This is what they did, I was able to watch while sorting things.
OK we went with WEP inscription at 128bit. My router at the house was using WPA2 encryption and we had to change that to WEP. Not my preference but that is the way it is.
Under wireless we made the operation mode infra. Made the wireless type mixed mode. Gave the SSID a name and adhoc mode 802.11g 54mbps.
Authorisation type is shared key, encryption type WEP and then put an encryption password into the WEP ID slot. Save and reboot.
Rebooted and then made sure we had the same WEP ID in the router/modem. You will need to reconnect afterwards by deleting the old network connection in the computer you are using to work with. In my case a laptop. Then reconnect that using the WEP ID password.
Then I went down to the observatory and made sure I changed the network (delete the old one first via network center) and connect to the current one with the new WEP ID password.
Downside is that if the computer in the obs goes down I cannot boot that (but UPS will sort most of that drama) anything back up. That also means the wireless router needs and small UPS to continue for external communication.
All this was done via team viewer and I watched it all while talking to tech support guy. From this experience I am really happy to recommend Scorpion Technologies. I bought those units two months ago and they asked nothing for the tech support. I rang them on a hunch that they might be able to help.
It would have (despite this looking fairly simple) taken me a while to cotton on to this. BTW Fred you were right.
Sorry Rally I was once again remiss with my detail. I must remember to be more informative in future.

With more info it might have been solved easily by someone here.