Three in the UK has a good deal with prepay data, 1GB of transfers for 10GBP
See info here:
http://www.three.co.uk/personal/prod...band_/payg.omp
You will likely need a sim for each country as data roaming is terrible.
Vodafone UK had a similar prepay mobile prepay but currently there is no info on their website... Can anyone in the UK verify if they dropped this?