Interesting question - and impossible to answer without a bit more background info. Still, I'll offer my thoughts anyway
Any school has the potential to succeed; a bit of a banal statement, I know, but what I mean is that being 10 miles outside of where it's happening needn't be detrimental to success, nor only having 3 classrooms. Three permanent (full-time?) teachers seems a bit excessive - you might want to consider getting rid of one and employing someone to work on a temporary basis during peak periods.
Being outside the main town you'll have to do some clever marketing to get EFL students to travel out of town. You may also want to invest in e-learning to try to gain students who do not necessarily need to be on the premises, at least not all the time. Short, closed courses could also be a good move - ESP/EAP/Business courses might work well here depending on the area.