Shopping Quarter, which as the names suggests is a shopping channel, has switched frequencies on Freeview.
The channel has moved from temporary multiplex COM7 to COM6 (Arqiva B). This expands the coverage area of the channel, and allows users of older standard definition equipment to view the channel.
A retune may be required if your equipment has not detected the change.
Correction: Shopping Quarter was in fact previously on the PSB3 (BBC B) multiplex. Although the move to COM6 has allowed non HD equipment to view the channel, coverage has reduced slightly.