The majority of them will follow suit. The ones most likely to resign the whip are those who have a strong relationship with their constituents and can make a case for them voting indie rather than sticking with the LP loyalty. I wonder, then, how much Jess Phillips has been cultivating her relationships with her constituents that she feels so certain she could resign the whip? And I wonder whether she's ever even thought about it in terms of loyalty to the party name.
You only have to look at the fact the seat here has remained staunchly Labour despite the parachuting of Trissy to see it's the party affiliation that matters. There will be exceptions, but they're exceptions that prove the rule.
If Trissy resigned the whip (he won't) he'd lose his seat without a shadow of a doubt. He's likely to anyway because Stoke's almost definitely going to be losing a seat in the boundary review, and I'm reasonably certain he'd be okay with going now his ambitions of front bench-hood have been briefly realised and then potentially taken away for good.
If Joan Whalley was still MP for Stoke North she'd be an example of someone who could potentially risk it (I'm not sure she would have, though, nor that she'd have still won), because she was generally well-liked for helping her constituents locally, but now she's been replaced by Ruth Smeeth...
You keep hearing this nonsense about MPs getting their mandate from the electorate and not the members, but it fundamentally misunderstands the role of party and affiliation/loyalty. 1) it misunderstands the fact that people vote for the party in the main (as explained above) and not for individual MPs; and 2) it misunderstands that with 1 being what it is it's the party selectorate who ultimately give the mandate to a particular MP to represent the party in that seat. Without the party these MPs wouldn't exist, and would certainly have never been elected. Perhaps it should be that the MPs get their mandate from the electorate, but that isn't the reality of party politics.