I use a "low-call" number...one of those that you dial a 0845 number, then the number you want to call. It is super cheap, and costs the same as any other low-call number...its the same idea as the "10-10-9-8-7" numbers in the States.
The number I use is: 0845-244-5445. When it prompts you, enter: "001" + area code + phone number. They switch out the number every so often, and when they do, they will tell you the new number to call.
It's 100% legit...I use it to call the family in WA state all the time, and my guy calls me from Scotland when I am in the States.
Good luck!!
Frances