@fletchwe
There are a few different threads about this behavior throughout the forum. Not sure if this is just a misalignment between Roku and Britbox or if it is user error in accessing their Britbox subscription.
If you signed up Britbox on the Roku channel, make sure you are accessing Britbox through the Roku Channel. If you signed up for Britbox directly with Britbox, then you need to access Britbox through their standalone channel/app.
Notice with the below images that there are two different methods to access Britbox (different channel/apps with different credential logins, not interchangeable).
Although I have not had issues with subscriptions purchased through the Roku Channel, many users would recommend subscribing directly with the subscription provider (Britbox) in order to avoid such issues that you are experiencing.
If you are sure that you are trying to access Britbox correctly, then contacting Roku Billing is best avenue to see what they can do regarding recompense. https://support.roku.com/contactus
Select the "Accounts, Payments, and Subscriptions" option from upper left.
Click on image to enlarge.

Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
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