anywhere to buy basic health, levitation, water breath potions etc.? emphasise potions, not spells.

Some of the temples have potion sellers, but you have to be a member of a certain rank to buy from them.

If I remember right: the Temple of Akatosh sells them once you reach fourth rank in their temple, some of the other temples sell them at second rank, and two temples (including the one in the town closest to the starter dungeon) don't sell them at all.

Been a long time, so I don't have more specifics.

Edit: If I remember right, the two temples that don't sell potions are Julianos and Kynareth (not sure about spelling).

Your can buy potions from temples if you are high enough rank, and make your own potions if you are higher rank in certain temples and guilds. But I'll say this: potions are not so ubiquitous in Daggerfall as they are in practically every other game. They are hard to come by, and frankly not all that great. Except for the one that restores your magicka. That one rocks.

Let me also say, though, that although you want potions and not spells, you can make very simple spells in the spellmaker that can be cast with very low skill. I mean, the lowest form of water breathing is very easy to cast, even for non-spellcasters. It's just that you have to get into the guild to use their spellmaker. There's also a spellmaker in the Temple of Julianos.