Hydrochloric acid: My hardware store sells 30% HCl as Spirits Of Salts, for removing limescale from toilet bowls. It's effective, unlike toilet bleach. It's nasty stuff, and if your seat-hinges are metallic, you risk corrosion. And remember to flush before you crap.

Sulphuric acid: No, hardware stores don't sell that here. You can get it from car batteries, and builders use the strong stuff for clearing drains. I have no idea how I could legally buy fuming sulphuric acid.

Nitric acid: Even less. Fuming nitric and sulphuric acid mixed gives you nitrating acid, which in turn is the gateway to nitrocellulose (and I suppose nitroglycerine), fulminate of mercury, and ghod knows what.

It's just as well that these latter two acids are restricted; if they weren't, I'm quite sure I'd have tried to make guncotton, and probably blown myself up.