Have had a great experience with Gomo, we have 3 x €9.99 accounts in our house.
My son has been on Gomo for over a year, and has been living in Spain since last August, and has not incurred a single extra charge, the included EU data roaming, is 10gb, and its been enough for him. He also had his phone stolen in December, just before he came home for xmas, we were able to cancel the old sim easily, and get a new one delivered in a few days. The first sim replacement, is free, and its €5 for each replacement after that.
Very happy with the service and the lifetime guaranteed price of €9.99.