Hello
Recommend you open up a general post or do some research about free dial up services in the UK.
ON the web there are a bunch, however, who knows whats good or bad. A lot of free dialup ISP have huge contention problems , i.e. you have to dial in a few times before you get access and the speeds are sucky (especially if you are coming down from broadband).
Once you pick a horse, try using the link above to setup the dialup component.
However, I would save yourself a lot of bother, and get yourself a cheap Ethernet nic for your machine and an Ethernet switch connect one into the other and have it connect to your brodaband modem If its a laptop of course this wont help.