Oh you sweet summer child.
The PLP is heavily populated with folk right of the membership. Thats why the right on the NEC always change rules to increase percentage of MP votes needed. The 20% requirement means no one with integrity or a backbone will get near it. Maximum 120 have a red line at disability benefits. Most times, standards/red lines wont be present and will be less than 70. The right get to choose who the membership can vote. So the vote will be between crap and shite.
You'll find yourself sadly disappointed. I imagine somewhat like Unison/GMB propping up the leadership only to get sidelined. Business interests have overtaken the party. Corruption is king. Your hope for improvement will slowly seep out of your body. I guess when describing decent folk as loony left, you'll probably not spot the irony. A right wing factional figure getting shat on by the right...