The default situation is that your chosen gas supplier will provide the tank - which it continues to own, thus saving you the capital cost which can easily be a grand or two. You are responsible for the costs of piping the gas to wherever it's needed, etc.
Indeed - but that's actually changed. When I had my original tank installed, that included (at no cost) pipework all the way up to where they installed an isolator valve where it enters one's house, and both ownership and maintenance responsibility for that pipework remained theirs - which was good for me, since it must be at least 50 metres of underground pipework! However, contracts have now changed, and their ownership and responsibility ends at the valve on the tank.
So while you wouldn't need to pay for the tank, you'd still have the cost of all the plumbing, the boiler, all the CH plumbing, etc, etc - so a good few grand up front.
Indeed - but, as I said, if one were 'starting from scratch' (e.g. a newbuild) one would also have substantial up-front costs with any fuel.
The downside to this arrangement is that only the one supplier can fill the tank - so you cannot shop around, you are tied to whoever owns the tank.
Well, it's not that different from other fuels - whilst one has a contract with one gas/electricity supplier, one can only get one's 'supply' from that once source.
Eventually, the government saw the idiocy of this situation, and rules were brought in that mandated the suppliers sell the tanks between themselves - so now people could switch suppliers, and the suppliers would transfer ownership of the existing tank.
Indeed, 'switching' LPG is now essentially no more difficult (or costly) than switching electricity of (piped) gas suppliers.
IIRC there's a limit on how often you can switch - something like minimum of 2 years with current supplier seems to ring a bell.
That sounds about right. There's certainly a substantial 'tank uplift charge' if one cancels a contract (without switching to a different supplier) within 2 years.
In practice, the need to 'switch' seems a lot less with LPG than with other fuels, since it seems that price is pretty 'negotiable'. I've always stayed with Calor, mainly with 2-year contracts. As each contract approaches its end, I look around, find the best quotes on offer and wave them at Calor - and every time (so far!) they have equalled or bettered the best of the competitive quotes.
Kind Regards, John