No solution yet.
Embarassingly, have remembered that my husband moved us from BT to Sky (to see if it would fix the problem - it didn’t!).
However, have realised that I now need to take this up on the Sky forum (and not on the BT one!)
Thanks for everyone’s help though - if I get a solution through Sky, will let you know - suspect it is an infrastructure issue.
Thank you for posting back to let us know.
With everything, you posted it does sound like it's a network fault. If you contact your service provider they'll be able to arrange for an engineer to be sent.