<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>
You gave him your WiFi password. If you don't now change it he will know it forever & you cannot prevent him from using it & connecting to your router.