the default is
admin
password

the default doesn't seem to work. People make a lot of fuss about changing your password, particularly that on the router so I may have done so. I have a word file that suggests that my Netgear password has been changed. It is in a code that means something to me, but that doesn't work either, so as I have this feint recollection of some IP address change that affected my router when I uploaded the ADSL2 firmware,  I am asking the collective if I should no longer use 192.168.0.1 for this login, but some other 192.168 address
cheers

If you can get to a login window asking for a username and password, then the 192.168.0.1 IP address must be correct, unless you have more than one router.

To be absolutely sure, open up a CMD (DOS) window and enter ipconfig.  The gateway IP address is the address of your router.
If you cannot remember the password, you can make your router forget everything by resetting it to its factory state, in which case the password will revert to its default value (given by Oldjim).  Poke the unwound end of a paper-clip down the hole at the back to press the small recessed button.  You'll need tor re-enter your Plusnet credentials to connect to the Internet afterwards. 

Back just before I upgraded the Netgear firmware to ADSL2, I did use a PlusNet supplied router temporarily to see if that improved the appalling speed I was getting at the time. Whether that is what is lurking at the back of my mind about the different 192.169- address, I don't know. but yes I am getting the login window from 192.168.0.1. Howevewr, all I get when I use it is the tab on the IE window just states 'Waiting for Netgear' (or something along those lines). Once I have posted this, I will log off the forum, then try accessing the router again, make a note of the message, then come back here to let you know what happened
Have just spotted ReedRichards post as I went to send this. I'm a bit concerned about resetting to factory settings in case it stops all the equipment I have allowed to use this router, but if I get really desperate, I guess I'll have to bite the bullet.
See you in a while

Would you believe, this time it let me in. I've added the address to the list of acceptable pcs, and now I guess the problem is solved. I've absolutely no idea what I did differently this time.
Thanks to all for your help