In response to the post by Ern, I am certain that every British built caravan with a bulkhead regulator is fitted in the vertical orientation with the inlet coming in at the top and outlet at the bottom.
The problem with the GOK regulators was the siting of the regulator which in a lot of cases was lower than the outlet of the gas cylinder.
The remedy was to lift the regulator to a higher location in the gas locker.
Whilst the gas still enters the system at the top of the regulator, the majority of the hose runs downwards to the cylinder, the small amount of downhill to the regulator was insignificant.
The use of single stage regulators removes the situation from happening as whatever enters the regulator is blown through by the gas, and any that may be present will run out anyway, and either be burnt away by the gas appliances or in the worst cases , after a lot of time, collect in the lowest pipework and need removing.
The GOK two stage regulator was that it kept being trapped inside the reg and caused the material surrounding the needle to swell and stop the gas flowing.