The visitors posted a respectable 206-7 after being put into bat, but Park seemed well on track in reply with captain Kamal Panchal (84) and Henry Newton (35) at the crease.
But tight bowling from Luke Mitchell (3 for 27) and Dharmesh Patel (2 for 30) strangled the midle order, restricing the hosts to 177-8 from their 40 overs.
The result left them second in the Premier Division, but further adrift of league leaders Queniborough.
Ashby Carington, meanwhile, remained in the bottom two despite a knock of 94 from opener Alan Smith at Houghton-on-the-Hill.
They made 206-5 from their 40 overs, but couldn’t defend them as the hosts squeezed home by two wickets, despite the best efforts of Ashish Didwania (3 for 37).
* Thorpe Arnold dented Sileby’s title challenge in Division One as they beat their high-flying visitors by 21 runs.
Half-centuries from Charlie Read (62) and Richard Garner (57 not out) helped Thorpe to 195-4 after they were put into bat,
And star turns with the ball from George Exton (4 for 21) and Myles Hickman (3 for 32) saw Sileby bowled out for 174.