Cynthia,
If you have a look at http://en.wikipedia.org/wiki/WRT54G, you can learn all about the model. You may not be able to get this through PCworld etc nowadays but there are always plenty of them available on ebay such a http://cgi.ebay.co.uk/New-Linksys-wireless-G-broadband-router-WRT54G-ct_W0QQitemZ330214606069QQihZ014QQcategoryZ44997QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
The sky router is normally a netgear dg834GT which is similar to the Linksys (Lynksys is part of Cisco which is one the major router/switch manufacturers in the world) but is for ADSL 2+.
Changing the firmware (or upgrading to latest version by the manufacturer) is always a good idea as it allows you to try to reduce problems.
If you do want to try it, just let me know and I can walk you through how to do it on a WRT54G.
Stuart