This is a quoted reply from Jodie at Cuckoo when I questioned their claim to supply BT broadband whe a customer on Trustpilot states they supply TTB,
Quote form Jodie at Cuckoo:-
"We do use the Openreach network however unfortunately there are a few providers that we don't have a porting agreement with (ie. Sky) which means we're unable to bring your landline number across to us. The same would apply to any providers not on the Openreach network."
The number change only applies to Sky and Virgin customers, exactly as stated elsewhere on the Cuckoo site."
Very evasive!