HOLD ON!
Dave, I assume Petra wants to be able to use the BBQ whilst caravanning, thus the device you suggest would not be practical or appropriate.
Using the Y pol, you are splitting the bottles output at high pressure, You would need two regulators, and some means of isolating the second leg, other wise it would mean turning off the gas at the bottle each time you needed to fit the device for the BBQ, and again whne you had finished with it to remove the fitting - not very practical nor particularly safe in the context of caravanning. The fridge would need to be relit every time.
A more practical appraoch is to arrange a Tee from the low pressure side of the regulator with an isolating valve, and a BBQ external fitting. For safety this must be fitted by a competent person observing the gas safety regulations