<p>See our <a href="https://www.bt.com/help/broadband/bt-cloud/getting-set-up/download-or-access-files/how-do-i-download-files--folders-and-devices-from-bt-cloud-">help page</a> for further information.</p>
Instead of buying a spare power supply why don't you just plug the old one in for the engineer visit and let him replace it? You'll still have the Vax one as a spare should it happen again.
