It's great I bought our mare for side-saddle but my husband pinched her for SJ! Highly enjoyable and so elegant and it doesn't do their backs in either loads of people think it does.
Check out the Sidesaddle Association (SSA) website: web page
I been doing it a couple of years and it is so much fun. There are "sideways" folk in Scotland too and regular shows around the country. I run the Sidesaddle area 8 (Surrey/Sussex/Kent) website: web page and as you can see we usually have a quite a lot going on.
The SSA have a list of instructors, so find one near to you and have a go. Once you get the hang of it, you wonder why we ever went astride!
Love it!! Cant wait to get a side saddle on my young cob, just need to find one wide enough for the little monster. I have shown several horses side saddle and I love it!!!!!