Ford KA cutting out when clutch depressed and now won't start at all

Thursday before last I drove my car and then popped home to change before going out again. I thought I was reversing down my drive as usual but when I went to go into first gear at the bottom i realised my engine had stalled. I kept re-starting the engine and it would start but was very juddery but then when i put the clutch down to go into gear it would cut out. We have checked the fuses and the electrics seem fine as the lights etc are working. We have also changed the spark plugs and put some petrol in (just in case the gauge was stuck, but it wasn't) but nothing has helped and then the car wouldnt even start at all. As the battery may have gone flat too we have tried jump starting with no joy. Any thoughts?