Have you noticed?
http://www.united-mobile.com/downloa...en_um+_eur.pdf
Area 5
EAST TIMOR, GUINEA-BISSAU, KIRIBATI,
LIECHTENSTEIN m, NIUE, SOLOMON ISLANDS, SOMALIA, SUDAN m, TOKELAU, WALLIS & FUTUNA
So, calling UM+ to UM starts from 1.29€/min from free-incoming countries. I suppose this pricing is "forced" by Jersey Telecom but it's sad UM couldn't do anything about it.
But in general, the UM+ offer doesn't look that bad. Almost all western and central Europe (not only EU) is covered with free incoming calls and outgoing calls to landlines and on-net are priced at 0.29€ (except for Andorra, Bulgaria, Liechtenstein where the rate is 0.59€). The only "expensive" European countries are Russia, Ukraine (no surprise), Faeroe and Greenland. No coverage in Belarus, Macedonia and Montenegro.
Of course, 0.59€/min for outgoing calls to mobile phones from the EU countries (even disregarding the setup fee) isn't any big deal to compare with "euroroaming" tariffs or Travelsim...