I posted here for advice so let me give a definitive update on using residential at a different postcode.  For those that missed my earlier post the background is that after three years as a homeless hobo I moved my kit into a house and switched to residential max.  I then needed to travel and took up the offer for the Roam mini kit but that unfortunately wouldn’t arrive in time and had to consider options.   Support advised that if I switched back to Roam  I would jeopardise my Mini deal that had not yet been shipped and if I switched supply address they couldn’t guarantee that I could switch back upon return if there was a queue at my postcode.  But they also said (and I screenprinted the exchange for posterity) that they probably wouldn’t notice a brief use away from the service address.  Not true.  I arrived, set up and it immediately alerted that I wasn’t at the service address and wouldn’t provide service.  I needed service so updated my address, used it for four days, returned and changed back four days later luckily without a charge or problem.  So for anyone in the UK, you cannot temporarily use your residential plan somewhere else despite what support might tell you.  And luckily my mini kit didn’t ship whilst my address was changed to a music festival!

An update to my earlier post; it ended well