Trying to figure out how to get a prepaid plan with a good amount of data that'll work everywhere in Europe isn't easy. Then there's issues about recharging the plan, and many of them don't accept foreign CCs, so you need to be in the country you purchased it in to buy a voucher from the carrier's store.

I also hadn't found any 'unlimited' data options on a prepaid SIM - they only appear to be on the more expensive contract plans. At least, based on my searches in France, Netherlands, Denmark and Norway.

Most of the prepaid SIMs I saw had heavy restrictions on tethering - can you point me in the right direction?