I've done this a few times. It's seriously piss easy and is very enjoyable. The only problems were I wasn't getting enough hours, and you do get the odd tricky question about English grammar. Are past participles a form of irregular verb? Fucked if I know, mate.
There's a bunch of Greek businessmen rocking up to meetings in the City in London activating their conversational English from Athens, sticking their hand out and saying, "bout ye, big mon, how's it hanging? Look, we're fucken skint, so do youse do tick? Square you up no prob'em like. Dead on."