@Suzybritain wrote: ... finally he said that Acorn TV WAS Brit box ...
For me, Acorn is listed on https://www.xfinity.com/learn/digital-cable-tv/svod/, while BritBox is not. Also:
Acorn TV is an American subscription streaming service offering television programming from the United Kingdom, as well as Ireland, Canada, Australia, and New Zealand. ... Acorn TV is owned by RLJ Entertainment, Inc.
BritBox is a subscription video on-demand service owned by BritBox LLC, a joint venture of BBC Studios and ITV plc. It is focused on British television series, featuring current and past series supplied from the BBC and ITV.