IF I had to hazard a guess as to what OFCOM will do, using previous history as a basis;
If Null refuses to block UK users from accessing the site, or give into whatever censorship demands they want to keep it open, they'll demand British ISPs (mainly the big providers) to force-block KiwiFarms from being accessed, I remember they did the same with pirating sites (Which spawned like a million mirrors of ThePirateBay and such). The issue is with these measures is that VPNs exist, there are many ISPs they don't bother checking in with (I'm with a smaller subsidiary of a major ISP, I can access sites blocked by other ISPs, like the aforementioned PirateBay) and ultimately, TOR exists as well.
They're also trying to ban or block VPNs, appearently "Just the free ones" for "The safety of our nation" but it feels like... They caused the problem and just keep 'fixing' it with more bans. Our nation literally operates on outright banning ''problems'' rather than fixing them.