It will not involve free movement so I imagine brexiters will be delighted (although Farage was very critical about CPTPP a few years ago i wonder if he'll change his tune... he said it was aspiring to be the EU on a global scale - so ichkeria's joke may not be so funny after all).
CPTPP is very likely to require a reduction in our food standards in order for British agriculture to remain competitive:
https://www.farminguk.com/news/food-standards-warning-as-uk-applies-to-join-cptpp_57506.html
Whichever path we now choose it will come with difficult choices.
But I don't reckon this kind of thing was important to brexiters... despite their protestations the vote to leave was all about reducing immigration. So long as that happens they'll be happy even if it means we're worse off. Oh well, we've done it now.