Hi,
For the UK these are probably the best ways - in order of increasing cost:
1. If your laptop has wireless networking built-in (remember the Intel Centrino "Blue man group" TV adverts?) then some cities, like Brighton, have free wireless Internet access for anyone - you just go along to one of the many access points (library is a good bet) - turn on and connect.
2. If you don't have wireless networking built in - Tesco and other places are doing good deals on wireless cards for laptops.
Do a Google search for Free Wireless Internet access in the UK - some coffee shops offer free access if you buy a coffee
3. Internet caf