Once you have decided to come along, you'll need to decide on accomodation. Believe me, a tent on one of the many campsites spread around the site is your best bet by far. A tent allows you to remain connected to the spirit of Cropredy, it's fun, it's cheap and there are toilets, showers and food at anytime nearby. Your middle-aged correspondent eschews camping at almost any price, pleading a bad back, an aversion to damp, a fear of tentpegs... yet for three days in August, he wouldn't be anywhere other at night than in his large tent, with the sounds of other music-lovers doing what they do at night as he falls gently asleep.
If you have no tent, or are coming from abroad, camping equipment can be hired. Phil Widdows mailed me to mention www.beansonline.co.uk and www.activeoutdoorandski.co.uk and both seem worth investigating.
If you really can't stand the idea of camping, there are many hotels and bed and breakfast establishments in the area, but they tend to get booked up fairly early. Anything within walking distance gets booked very quickly. Take a look at www.banburytown.co.uk/accom/ for some of the accomodation nearby.
If money is not a large consideration, you may want to investigate hiring a canal barge. They are not cheap, but barges can be moored at Cropredy. Please check that you can moor the barge there for all three days, and try to find out how early you will have to arrive - lots of them turn up for the Festival. The agency you hire the narrowboat from should be able to advise on the above points. It wouldn't be right to recommend any one hire firm, it's not ethical, and none of them have offered me any money. However, www.google.com will find lots of them. Honestly, you really would be best to take a tent.