If you are going to get into technical diving, your true experiences will not be in the Blue Hole but in nearby Rock Lake. It isn't much different, though--it will be a few degrees colder in the winter. The coldest I have experienced there is about 58°. It' mainly just a heck of a lot bigger and a heck of a lot deeper. There is, however, no facility for warming up there--the site is pretty much a big, deep swimming hole in the prairie.
You need to be under the supervision of one of the tech instructors with permission to dive there. I will be there doing a trimix class in November, and I will be quite tied up during those days, but I come there with some frequency. Join us some time and you will see a variety of dry suit options and hear a variety of opinions, depending upon who shows up to dive then. Send me a private message and we can make arrangements.
You need to be under the supervision of one of the tech instructors with permission to dive there. I will be there doing a trimix class in November, and I will be quite tied up during those days, but I come there with some frequency. Join us some time and you will see a variety of dry suit options and hear a variety of opinions, depending upon who shows up to dive then. Send me a private message and we can make arrangements.