Dave Liquorice wrote:

lugging cylinders that aren't far short of 100 kG (2 cwt,
15 stone) when full as you buy 47 kg of gas.

Don't think so, flogas say the tare weight is 34kg

https://www.flogas.co.uk/shop/cylinders/flogas-gas-cylinders/47kg-propane-gas-cylinder-refill