If you use Hyponex make sure you mix in stuff to lighten it up, its HEAVY, compacts very easily, and dries out quickly. I got a few bags and ended up throwing them in my compost.
I use MiracleGro soil even though most people avoid it like the plague, my plants are doing well with it.
i used West's. was like 3quid for 2 packs. its great. organic, no bullshit in it. no fertilisers or anything, no chemicals, just soil with natural bits in it kinda thing.
its really good so far anyway, i need to water my plants about every 2-3days with it, it does hold the moisture quite well.