With regards to gas bottle deposits check around different supply companies as some do no-deposit bottles over a certain size (it used to be 14kg at one I use but not sure if it still applies). Calor seem to always charge a deposit regardless but theres always empty bottles on Gumtree /free ads for either free or not much money. A good ask around with people you know and you can usually source one for free.
Regulators and hose are cheap on ebay and don't forget your lava stones.