The Bucks started the livelier with Sean Clancy and Andy Todd combining well, and it was Todd that sparked the breakthrough for the hosts with a mazy run that caused Martin Rice to spill the ball, allowing Mike Grogan to slot into an empty net.
Torquay equalised after 18 minutes when Angus MacDonald met Luke Young's corner and made no mistake from close range.
United took the lead after another splendid Young corner, this time met by Ryan Bowman, who duly converted.
Just as the visitors thought they had done enough to go into the break with a lead, Telford equalised with Rob McDonald nodding in from a Clancy corner.
After the break, Torquay went down to 10 men as Ajala was given his marching orders having received his second yellow for a foul from behind on Ryan Higgins.
It didn't take long for Telford to make the most of the numerical advantage. Higgins's long throw wasn't dealt with by the Torquay defence and Steve Akrigg was there to edge a looping header over Rice and put the Bucks back in front.
Chris Hargreaves's men refused to be beaten, however, and just five minutes later they were level again. Telford were once again undone by a set piece with John Wakefield bundling the ball in at the near post from another corner.
Torquay's resolve was finally broken with just eight minutes to spare. After failing to defend a free kick, Adam Farrell was gifted his goal from inches out.
Frustration was clear for the visitors when Downes went through the back of Higgins and was duly shown red in the dying minutes.