Calor “Patio Gas” cylinders have a 27mm outlet valve.
If your caravan has the historic type of UK gas system where a regulator is attached to the gas cylinder and a low-pressure flexible hose (with jubilee hose-clips) connects that regulator to the caravan’s metal gas pipework, then (as Anseo has advised) a 27mm clip-on regulator should be used (example here)
However, if your caravan has the more recent type of gas system where a 30mbar regulator is bulkhead-mounted and a high-pressure hose (‘pigtail’) connects that regulator to the gas cylinder, a UK butane-type pigtail (example here)