My husband and I had nearly this same problem when I was in the states and he was here in the UK. We both (now) work for a VoIP (Voice over Internet Protocol) company and if both ends have compatible phones that are correctly configured, calls are completely free. For this though, you do need broadband, but you can remote in (and apps such as Fring and Bria also work on our platform quite well). Calls to US numbers from the UK through our platform are 1.5p per minute. Also, if your family in the states has free long distance, a US number with us (to route the calls through to your UK number) is £4.99 per month. I've probably made it more confusing than it really is though...
I loved being able to pick up my cordless phone in the states and dial "202" and get a direct line to my husband, or "200" for his mobile. All it cost for us was the price of two VoIP phones (we wanted cordless so we picked the Gigaset A580IP model, which can also be plugged into the landline).
I am NOT advertising for the company I work for, but if you'd like more info on it, please private message me, as I will NOT be posting the name of the company here.