Poly were never ahead at any point in the four periods of the game. Wanderers had a two-goal lead no less than four times - including an 8-6 advantage when Jo Jenkins-Delf scored from distance early in the last quarter.
A goal by Justin Tubbergh brought Poly up to 8-7 early in the final period. Had Wanderers managed to convert a man-up chance shortly afterwards, they might well have won through. But the London side survived that scare and pulled up to 8-8 through Chris Icely - leaving a penalty shoot-out to separate the sides.
Both teams had one of their five shots saved, taking a thrilling match to 12-12. At 13-13, the Welsh shot again - and missed - leaving Liam Neill to slot the winner at 14-13.
Manchester qualified for the final by defeating Sutton & Cheam 11-7.
Photo: Tim Rezelman scores a penalty for Poly against Wanderers in the second period.