George Thomson's late header further cemented Town's place in the National League Playoffs and ensured maximum points were taken from a first trip to Havant & Waterlooville.
Despite falling behind to Matt Paterson's penalty, Michael Woods capitalised on a defensive mistake to level before half time.
Town created chance after chance in the second half, though had to wait until the 81st minute to take the lead when Thomson got his head to Jack Muldoon's cross to claim the winner.
Simon Weaver made three changes from Saturday's draw with Maidstone as Liam Kitching, Thomson and Woods took the places of Ryan Fallowfield, Mark Beck and Liam Agnew.
The first chance of the afternoon fell the way of the hosts when, after Dan McNamara had won a corner off the legs of Kitching, Belshaw made the first save of the contest.
The save was bettered in the 19th minute as Belshaw showed excellent reactions to tip Alfie Rutherford's effort over the bar.
Both goalkeepers were impressing in the opening 20 minutes of action as Laurence Bilboe showcased his abilities, denying Woods' attempt from just outside the area.
Seconds after the save Town conceded a penalty when, despite looking to have won the ball, Lloyd Kerry was judged to have fouled his marker, allowing Paterson to open the scoring from the spot.
Town respnded by getting on the front foot and testing Bilboe through Jack Muldoon's near post shot, before Kelvin Langmead headed wide another attack.
The equaliser arrived three minutes before the break when Ed Harris tried to head a cross back to his own keeper, but ended up putting the ball past Bilboe, who managed to recover and claw the ball off the line, but only into the path of Woods to tap home.
Weaver's side made a positive start to the second half, creating chance after chance, though Muldoon could only loop his finish over the bar after being played in by Agnew.
Agnew then had a chance of his own, though Harris blocked his shot, before Bilboe made an impressive flying save to keep out Muldoon's powerful drive.
Warren Burrell was next to go close after dribbling into the box and trying to squeeze the ball in, only for Bilboe to extend a hand and deny Town taking the lead.
The attacks continued through Thomson who saw a shot dfelect behind for a corner, before almost bending a spectacular long range effort into the top corner as the tie entered the final 20 minutes.
Woods and Leesley both went close, before Town got a deserved second with nine minutes of normal time remaining.
A great ball from Kitching had released Muldoon, who had the composure to float a cross onto the head of Thomson to score the winning goal.
Town: Belshaw, Falkingham, Howe, Burrell, Thomson, Leesley, Langmead, Kerry (Agnew 34), Muldoon, Kitching, Woods (Thewlis 87)
Subs not used: Fallowfield, Beck, Cracknell
Goals: Woods 42, Thomson 81
Havant & Waterlooville: Bilboe, Williams, Harris, Fogden (Jalloh 66), Paterson (Quigley 66), Rose, McNamara, Rutherford, Cordner, Donovan, Paul (Lewis 82)
Subs not used: Woodford, Carter
Goals: Paterson 22 (p)
Referee: P Howard
Attendance: 937 (40 away)