I tried On-speed a couple of years ago. It worked amazingly well for the first couple of weeks and then, for some reason, became a millstone around the neck of the dialup speed. Decent people running it though - gave me a full refund without argument.
In the absence of a wifi-enabled laptop, looks like my best bet is either a USB dongle, or a wifi PCI card then?
PS The excellent 7day shop is offering a Bluetooth Wifi Dongle for £6.49 - will this do the job, or should it not be bluetooth?