Bruce, I don't recall there being any rules against flash photography in the conservatory. The place was similar to a green house and bright enough inside so there wasn't much need for a flash in most of the pictures I took. I did use the flash a few times when trying to get a shot of one amongst the greenery and saw other people doing likewise.
The only rule I did see enforced was no touching the butterflies or enticing them to land on you. If they did happen to take a liking to you and lite on your head or wherever it was fine. Just don't try to shoo them away as that would be touching. I had one land on the back of my neck and had to resist the urge to slap the little bugger off.
