Weedons got handy contributions throughout their batting order, led by top-scorer James Watson (56 off 75), and headed into the change of innings confident they could defend 224.
And when they had Cheviot reeling at 47/3, they felt they had the game under control.
But enter Darling. The Magpies' batsman has had a breakout season and teaming up with Angus Sidey (55 off 65), ruthlessly put the game beyond reach.
He raised his bat for an unbeaten 100 and led his team off for a fine six-wicket win, securing their spot in the semis.
At Sefton Park, the Sefton Seals made short work of visiting Lincoln, knocking off an easy seven-wicket win.
Right-arm paceman Micah Campbell knocked the top off Lincoln's batting, snaring four wickets, before Canterbury first-class seamer Fraser Sheat mopped up the tail.
Chasing just 114 runs to win, recruit of the season Amandep Arora smacked another brilliant half-century, ending up with 63 off just 34 balls.
Oxford-Rangiora were decimated by Covid-19 and were forced to default against Leeston-Southbridge on Saturday.
But it was ever worse news for Southbrook, however, with the 2011/12 champions having struggled for numbers for the past few seasons and pulling out of this year's competition.
They defaulted their match against Ohoka and the stalwart club now faces a real struggle to survive in Canterbury Country's top flight of club cricket season.
Darfield had the bye.
Short scorecards:
Weedons 224/10 (J Watson 56, C Robson 35, S Clarke 35, B Coburn 32; C Cameron 2/27, T Fitzpatrick 2/33, W Anderson 2/44, W Smith 2/46)
Lost to Cheviot 226/4 (H Darling 100no, A Sidey 55; C Robson 2/39).
Lincoln 113/10 (J Eggleston 27, B Moore 24; M Campbell 4/33, F Sheat 2/13, J Jones 2/31)
Lost to Sefton 116/3 (A Arora 63, L Taylor 23; B Moore 2/31).
