No idea if it’s a current offer only, but checking subscription settings on iPhone they have annual subscriptions for £29.99 and £59.99 - I’d buy at £59.99 but for under £30 seems a bargain currently. Can’t see there’s any real difference.
Content has gradually increased in the UK over the last couple of years, I use it on an AppleTV. Don’t have issues with closed captions, though there were some glitches with audio settings and no video just audio a couple of years ago.
I think it’s now good value if you enjoy the content. Perhaps content is more limited outside UK.
I tried it for a few months at the start. Then took a break for a few months and now I’m back again. With NETFLIX serving the Kill-em/Zombie/Shoot-em genre and Britbox serving the more cultured genre (plus iplayer) I find all the boxes are ticked.
At the start the interface was bit clunky but it seems fine now. I do get peeved though when, occasionally, it will want me to reverify via the web site 'cause then I have to power up the PC &c.
It can still take half an hour each night finding something to watch though!