I can only go on what their policy document says on the net and which includes an exclusion clause in respect of any claim for – “Loss or damage to the Caravan and its Contents unless kept whilst not in use within the boundaries of Your permanent home or other location as notified to and accepted by Us.”
So, when you bring the caravan home it is “in use” and would be covered, unless somewhere in their policy “in use” is defined as being used whilst away from home on holiday.
To make sure that you are covered I would raise the issue with the insurers, and secure their agreement that the exclusion does not apply when you have the van at home getting ready to go away, or for cleaning, repairs maintenance etc.
At the end of the day, it’s all very well what we may say on this forum, but in the event of any claim it’s what the insurers say that matters and it is therefore best to cover yourself
Phil