At that price, it's worth buying one and taking "Just in case".
We've been (to France) twice so far, and haven't needed it, as many sites have the "commando" socket as per the UK.
We're planning on overnighting en-route in our tent next month (as opposed to a hotel), more than likely on municipal site(s), so who knows, maybe we'll get to use it this year.
------------- 2015: 19 nights/8 camps so far.
Planned Sept: 13 nights at RCN La Ferme du Latois (+ 2 Overnighters)
2014: 34 nights/10 camps
2013: 36 nights
2012: 23 nights
You’ll love a Champion when caravanning! Quiet Petrol and LPG Generators