OK,
So I suspect you are currently connecting via a USB connection and an ADSL modem, probably supplied by Tiscali when you signed up.
You need to work out if your laptop has a wireless interface already - if not then you'll need to purchase one of those too, and get it configured. If you can tell us the make and exact model of your laptop we can probably look it up and tell you ...
There are two options - a usb interface (which looks very much like those little USB pen drive things) or a PCMCIA (thick credit card looking thing).
The USB interfaces are a tad cheaper and easily ported to other machines; the PCMCIA interfaces are better integrated BUT they don't fit in PC's and they have a habit of getting the aerial bit snapped off when you drop the laptop ...
http://www.ebuyer.com
Netgear DG834G (quick code 52244) wireless basestation with ADSL interface.
Netgear WG111 (quick code 60014) USB wireless adapter.
Netgear WG511 (quick code 46056) wireless PCMCIA adapter.
Linksys WAG354G-UK (quick code 94178) wireless basestation with ADSL interface.
Linksys don't do a cheap wee USB adpater (they have cheap chunkier ones, but these are no good for you), so I would go with the netgear one if you want USB.
Linksys WPC54G-UK (quick code 45024) wireless PCMCIA adapter.
Let us know the make/model of your laptop and we should be able to close it down ...
Robin