Builders merchant. £6.99 for 5 liters of 30% hydrochloric.
I get caustic crystals from the hardware store, and ammonia too - still sold by cleaning brand firms.
There's plenty of caustic in 'Mr Muscle foaming oven cleaner' too, but at ten times the price.
Not sure about sulphuric - battery acid - halfords?
There are chemical wholesalers everywhere, but do you really want 25L of acid sitting in your shed? If not, you need to find a trade that uses it and breaks it into smaller packs. E.g. french polish suppliers stock a lot of common chemicals
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