i've been before, 2 or three years ago.
i went for the whole weekened:
saturday -
outdoor practical session - split into appropriate groups of refereeing ability/level, run by select group refs (mason, pawson)
RA quiz - we won!
RA dinner - wayne barnes was the guest speaker (rugby union top ref). i got quite drunk and was pretty hungover for the classroom sessions the next day!
sunday -
the classroom sessions were run by (the ones i went to) taylor, mason, lee betts and a few others i cant recall
was an enjoyable weekend, obviously loads of refs from all over the country all at various levels. there's also a decent old stock / end of line kit sale which was good