As I said previously you can get there with one of the official coaches, easy, reliable, a no brainer really... If you have a car that's an added bonus, bare in mind though that the car park for festival goers is a bit of a walk. You'll be dropped much closer if you use one of the official coaches. Another option is the train and bus. They leave from Paddington and Victoria, it will take you between 1h30-2h30min depending on which train you take. Evidently, the slower, the cheaper so it's up to you if you want to save some pennies or some time. Time is money my friend. Your train will arrive at Castle Cary station, from there you can hop on a free coach direct to the festival. This will take you approximately 15-20min.