Not sure about the quality/max/continuous power output of the Makro one (besides you need a trade account to buy from them) but I've been doing some digging on the internet to see if it was as good a bargain as it seemed and found this on eBuyer:
http://www.ebuyer.com/product/127785
650W (800W max) 2 stroke petrol generator, £44 inc VAT. With next delivery it works out at £59.27 but they are advertising free delivery on orders over £50.
I'm amazed, I'm used to generators costing a couple of hundred. These are cheaper than a decent 12v battery.
Are there any noise restrictions at events?