You should be ok with Turbo / Astreas and definately hermits. The Ceriths will depend as they can go quick sometimes after delivery day, not all LFS by me stock them.
Nassarius really are a pain to get, if your LFS gets them in they are likely to go out of the door just as quick. Most of us ended up getting them online as I say. Fishmans frags is also good for them.
Possibly a phone call to see whats in stock before you go trecking may be the best idea. Sometimes aswell, if you are paying postage on one type of snail, ie nass, it makes it more worth it if you combine the buy with something else. Thats what I tend to do. Trawl the websites for what I want then see what else they have in stock so the delivery charge is worth while.