Its not a HUGE park, but its fairly sized,
If it's anything like the other 'festivals' held there, you won't need to get there early or anything, as they're free concerts, and arent like cordoned (sp?) off, so you can just walk around the crowd to get to the front line
http://img378.imageshack.us/img378/9069/beaconuo8.jpg
Thats a quick image i knocked up using a screen shot of google maps

(stage isn't to size, but thats the part of the park the festival was in last year)
That part of the park is also in like two levels,
Becuase its normally loads of football pitches, so its a way of dividing it,
So if worst comes to worst and you are at the back, then you'll still be able to see over everyone
