I'm going to be in Paris for 5 days at the end of next month, and have scoured the information in various threads here (including the main prepaid data SIM card one and the France/UK one). I'll have my Verizon iPhone 5 (which should be unlocked on international GSM carriers) and a factory unlocked iPhone 4 as backup if needed. I'd really like to have data, about 200-300Mb should be sufficient for those 5 days for email/maps/etc but it'd be great to have 1Gb and not worry about usage. This would be really easy in the UK with a giffgaff goodybag. Voice is needed but minimal use (so no data-only SIM).

I see that it appears to be easy to pick up an SFR or Orange SIM card once in Paris, but reports of it taking a day (or even two) to activate data has me hesitant in counting on this. In addition, I'd really like to have it activated and the number known before I leave the US.

I've found a couple of great plans through Sosh (an Orange MVNO) and SFR's Red Series, both have nano-SIM's too. It's 20-25 Euros for a month of 1Gb-3Gb data (even 4G speeds perhaps) with unlimited calls and SMS. This would be SO perfect and reasonable; does anyone have any experience with either of these? Any way to get it in the US? Looks like it'd be a real hassle to get even in Paris.

I'll also be in London for a day at the end of the year, so I could perhaps hang on to this and roam - data will be expensive, but it's only a day so I can keep the usage fairly low.