After Freeglobalsim took my money and ran, i went ahead and gave more money for charity this time to CallBlue .
To my horror I found out (now that my prepaid credit has been exhausted and the sim card is blocked!) that they actually DO charge for roaming!!!
you wont find this on their home page or in their rate table!
it is hidden nicely in the terms and conditions that their "fair use policy" implies that after 10 minutes of an incoming call, they start charging 10p/min.
Someone should up update
http://www.prepaidgsm.net/en/international.html as it endorses a card that doesn't really provide free international roaming.
So.. are there any hidden roaming costs after 10 minutes also with UM+ ?