Thanks ProfJohn, agreed, but gas flows freely from the tail pipes when disconnected from the reg. and the appliances operate normally when propane is connected.
When the reg. is disconnected from the caravan feed and screwed onto the butane tail no gas comes thru.
Comment from the local caravan servicing chap, 'bit of a nightmare, seems impossible, sorry can't help'.
The butane is a few years old, could that be a problem?