2004 clio didnt start first time then it did start with idling revs of 2000 and no power. Drove to garage at about 20mph where he fitted a new alternator (and serviced and mot'd it). Drove fine home and out this morning but now wont start and petrol light on. when i checked how many miles since i filled up all the record lights, mpg etc, all showed nil. The engine turned over weakly before dying. Any advice please