You should have a look at www.1stdial.com you can have far cheaper calls driect from your mobile than these MVNO SIMs. You can buy a locally, set up on the web and dial direct from your mobile. Most European countries are 1p compared with 4p on the MNVO's. Don't lose your main mobile network benefits either.

Lycatel is only doing what Lebara mobile , another company starting with N , (cannot remember the name offhand) and carphone warehouse started doing long back. Considering the large immigrant populations in cities like london who do not have exclusive access to a landline to use calling cards, cheap international mobile calls by MVNOs is a very welcome step. I made a mistake of calling overseas once using O2 and was charged 100 times of what skype would have charged me for the same call.