Try this Directory which should help you identify some packs nearby to contact. Most packs nowadays also have websites which is a real bonus!
http://mfha.org.uk/pack_directory/
I love this forum. I have just spat coffee all over my desk laughing at this post! I shall definitely be more cautious about where we stop on our next foray to the west country lest we be jumped by rampant Dorset residents!
Whatever gloves you have. I have a white string pair and a brown leather pair, which have both been fine. See what looks best with with your brown tweed.
Any colour shirt will be fine, but wear a coloured tie rather than a white showjumper's tie. If budget is an issue get a cheap school shirt...
Facebook is in trouble again for not removing a video that showed a baby being abused. Apparently it did not breach their user conditions
Interesting report by Ch4 news.
https://www.facebook.com/media/set/?set=a.279648318720843.77508.135682489784094&type=1
It looks like everyone is wearing traditional hunt dress for this event. Pale breeches (beige colour if you have them) with your tweed jacket. Then either a collar and tie or a stock shirt and coloured...
One of my military friends came to a hunt ball with me he wore mess dress and he was a magnet for every girl in the room! He admitted later that he had packed black tie in case he felt like he was sticking out too much!
I'm assuming you already have the Fitzwilliam on your list! (if you need photos I have some you can utilise)
There was an article in The Field a few months back listing hunts with theatrical leanings. I may still have it and will try and unearth it, but not making any promises.
It was a close run thing - hounds were drawing up and down the river. The leads were stretched right across my path and I just managed to hurdle over them in time. Except nobody else can see them, so it just looks like you are running around like an ungainly troll....