It depends on Sky's T & Cs.
Some ISPs take the issue of a MAC as the start of the notice period, others require separate notice. Complications can arise if you don't migrate within the notice period, particularly if it is separate notice. Usually, with the implicit notice, not using the MAC causes the notice to be cancelled and service continues as normal.
Whatever the T & Cs, it is always wise to notify the losing ISP as soon as the migration is complete. They should be told by Openreach, but some ISPs make out they weren't told. Whenever I've confirmed I've moved, my old ISP support have always said "Yes, we know, thanks".
My broadband basic info/help site - www.robertos.me.uk
| Domains,site and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 56.6/14.1Mbps @ 600m. - BQM
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.
Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.