prepaid internet access for laptop (WWW and e-mail)

Hello,

I would like to buy mobile internet access for my laptop
for 2 weeks in May 2011 when staying close to Marseille
(I am living in Germany).
I own an unlocked Hotspot 3G+ (Huawei E5 , E585) already
( Unlocked Wireless Modem Huawei E585: Amazon.co.uk: Computers & Accessories )

Would appreciate help on the these issues:
a) a prepaid plan with SIM card , e.g. for 2 weeks or 1 month
b) unlimited internet access 24/7 (at least 5 GB) for WWW and e-mail traffic

Many thanks in advance

Andreas