On Tue, 19 Nov 2019 19:10:21 -0000, NY wrote:

I was told by the company that we buy our gas from that gas safety laws
prohibit the customer from uncoupling the hoses and replacing cylinders,
and that only authorised, qualified people (their drivers and also
central heating plumbers) are allowed to do it.

Well that's one definition of "competent person"... the one that Gas
Safe or others with a vested interest like to push. Bear in mind that
"LPG work" requires another tick in another box on someones Gas Safe
ticket. So a bog standard "central heating plumber" may not be
"authorised" as their ticket is for domestic natural gas.

How does it work with cost if you obtain your own cylinders? Do you pay
a deposit for the cylinder itself ...

If starting without a cylinder yes you pay a deposit and for the gas.
The deposit is refundable but you'll need the bit of paper to show
how much you paid and I'm not sure that you can get a refund from any
place selling full cylinders.

It's normally easier to obtain a cylinder from some where (word of
mouth, freegle etc) for nowt or a few beer vouchers if it has a
useful amount of gas left in it. You just take empty cylinders to a
seller of full ones and exchange it for a full one for the price of
the gas.

--
Cheers
Dave.