Note that the card renewal only applies to subscription users - it does not affect Freesat cards as far as I can tell (and others agree.)
Your contract with Sky - subscription or FreeSat - says it can only be used at the address for which the card is registered, so contractually you cannot take it in the 'van. Having said that how can they police it if, like FreeSat, you are not required to have a phone line connected? What is more whichever type of service you have you own the box from day one so you are covered if you take the box with you but leave the card at home.
Simple solution - get a Freesat box instead.