Hi
There are a couple of ethernet modems that can be attached to a router but not many.
The speedtouch 330 is a usb modem which cant connect to a router so you need to purchase a combined adsl modem router which will connect to the PC via a network card (ethernet).
If a laptop is also involved then your best best would be an adsl wireless router and you set up would be something similar to this
http://www.kitz.co.uk/adsl/wireless.htmTheres a vast choice of adsl routers available on the market depending on your budget.
One of the ones I most commonly recommend is the Netgear DG834G - its pretty reliable and has a good interface for a newcomer to routers.
The last time I looked the cheapest place to purchase it was amazon who were selling it with a free usb wireless adapter.
If this is a bit more than your budget... or you have a specific router in mind, ask on here and we will tell you if its right for the job, as its easy to purchase a cable router by mistake (something Ive known PCWorld recommend more than once) :/