Firstly i am a customer like yourself self and am bitterly disappointed about the Youview NowTV App being reduced to 25fps when watching Sports on a Boost Pass (lets hope temporary and NowTV sorts it out).
The Youview Boxes with a Boost Pass was originally running at 50fps for Sports when using the NowTV App on the Youview boxes.
I have a Youview Box with a Boost Pass and 50 fps was playing up to about two weeks ago, where NowTV had to temporary reduce it because of on going sound drop outs and buffering when watching Sports on the Youview NowTV App in conjunction with a Boost Pass.
I am not a BT TV customer, but if you are a BT TV customer and subscribe to the NowTV bolt on packages via BT then have you tried watching live Sports through the main BT EPG television guide instead of the NowTV App where the picture quality and frame rate might not be effected (if you are not a BT TV customer then you are stuck with the NowTV App like me).
All i can suggest is submit a complaint into NowTV.
Only you can decide that, let your eyes be the judge.
If you only watch sports and not interested in movies or entertainment at 1080p with 5.1 surround sound or the extra additional stream is not important to you.
Then i would say definitely yes cancel the Boost pass until NowTV have resolved the reduced 25fps frame rate (where i am guessing your only supported 50fps device is a Youview Box ?).
My opinion 25fps looks horrendous for Sports and is a night and day difference when you can watch at 50fps.
Where with the bump up from 720p to 1080p in PQ to my eyes it is only marginal and not a Night & Day Difference unless you are watching on a larger 55inch plus TV or Projector screen.
Been watching the International Rugby on Amazon Prime during the weekend and Amazon are streaming it in 25fps and it looked shocking 😠.
When Amazon Prime had Premiership Football for the First Time, quite a few of the games being streamed was available in 4K UHD at 50fps and the picture looked sublime.
Anyway hopefully once NowTV finally resolves the 25fps playback on the Youview box for sports you can also reactivate your NowTV Boost Pass if you do decide to cancel it.
I have a Youview box, but luckily i have other supported devices that plays 50fps sports on a Boost Pass.
I still keep hassling NowTV from time to time about the other 5 Sky Sports channels that are still fixed at 25fps and had a moan or two about Bonus Streams and VOD sports also stuck at 25fps.
I think i have found out why i was only getting 25fps on Amazon Prime whilst watching the Rugby over the weekend.
Was using the Amazon Prime App on my new 4K Android Philips TV and for some unknown reason it was only streaming 25fps over Ethernet (even though i have watched 4K HDR movies which look great on Prime on the television inbuilt App).
Just tried my Youview box this morning and compared the live tennis with the Amazon Prime App on the Philips TV and the Youview Prime App was playing 50fps with a fantastic picture.
Where the Prime App on the Android Philips TV was playing back at the horrendous 25fps frame rate and the picture looked horrible.
When the next round of Rugby is available on Prime this weekend i will be definitely watching on the Prime App on my Youview box and hopefully it will be 50fps like my short test with the Amazon Prime tennis which i don't normally watch (not being a tennis fan).
NowTV removed the red service banner about an hour or so ago.
Also over on the Youview Community Forum, there is an official reply stating that 50fps has been added back to the NowTV service via the NowTV App with Boost when watching sports.
Glad this has finally been sorted for you it has certainly took them long enough to get it resolved. Hopefully now they can focus on getting 50FPS to all the Sports Channels and On Demand content.