Cold Weather Caravanning

I have a 1991 Swift Corniche that has been fully restored since being in dry storage for 20 years.  Before use it was fully serviced and had a gas and electrical safety check, which entailed replacing all the flexible gas hoses, the regulator and 1 of the hob burners, tyres, brakes and all the window seals. It is a great little van, great fit and finish when compared to some of the "new" van's on the market.  My problem is this: this weekend, as the outsidel temperature dropped from 12 to 7 degrees Celcius, the gas appliances became unuseable.  Only 1 burner at a time would work, only the oven or the grill and the Carver 3000 blowh air heater stopped all together.  I at first suspected that the new regulator was blocked and went to remove it, then I saw that the gas bottle (as small 4.5 kg Butane cylinder) was white with frost! On removing the regulator and turning on the bottle tap, only a faint whisper of gas came out. Is this the reason for low pressure?  After warming the bottle with hot water from the shower block in the morning, some pressure was available but quickly dropped off after making breakfast.  How do I prevent this from happening as we do want to use the van in November for a fishing trip to the Broads?