1988 Jaguar XJS why won't she start?

Hi, Please can anyone help? I ran out of petrol (I think) and also think that I ran out of LPG gas which my xjs has run on fine until now, whilst going to the fuel station for LPG the car seemed sluggish so i switched to petrol (which was also very low) It ran fine for about 4 miles, then stopped. I put 10 litres of fuel in, it ran for about 1 mile then stopped and would not start again.
I have tried and tried to start it since but without any luck. I must admit I am a bit (lot) clueless when it comes to cars, can anyone help please?