Luke Betts' side have now won 12 of 13 league outings in the Thurlow Nunn Youth Central Division, drawing the other.
Dennet (8') and Youngs (33') gave the league leaders the lead, though James Coton's brace (39', 68') wiped it out.
Flynn Bobby (79') turned the game on its head, heading home at point blank range for an important win for the young Marketmen.
Jim Gregory (3') saw a close range shot from the left-hand side deflected just wide, while Riley Dennet's following corner was on target only to be denied by Bloom.
Flynn Bobby (5') however was fed into space down the left wing, whose low cross was cut out for a throw in, though Dennet intercepted an under-hit back pass (8') to slot into the bottom right-hand corner.
Brad Smith (9') in reply hit a low strike straight at the keeper from outside the box, as Flynn Bobby (10') jinked into space on the left-hand edge of the box only to fire narrowly wide of the bottom near corner.
Needham arguably had the better of the possession since the goal (16'), Charlie Smy was found after neat passing unmarked outside the area only to fire just wide of the bottom left-hand corner.
Jake Bloom (17') meanwhile was on hand to re-adjust and divert a long shot behind for a corner, as Needham went close (20'). A partially cleared Bobby right wing corner fell to Evan Gledhill to loop a clever side-footed lobbed strike at goal, though the keeper reacted well to just hold on his line.
Harry Hopkins (22') drew a smart stop from the keeper soon after, the midfielder's ferocious strike from distance was tipped just wide of the bottom left-hand corner.
Bobby's resulting corner caused more havoc, albeit flick on at goal was deflected agonisingly just wide of the bottom far corner - which Bobby's set-piece was headed just over at the far post.
Great work from Oscar Wakeling (24') won back possession high up the right wing, which James Coton latched onto the loose ball to play a smart one-two with the former to drive freely into a shooting position, but to slice his shot wide.
Wakeling (26') then received the ball in space to shoot, which was blocked.
Needham continued to pile the pressure on (28'), Brad Smith's clever throw released Gledhill down the right-hand side, spinning his man excellently to cross for Wakeling who controlled it well but shot just agonisingly wide of the top far corner.
Hadleigh (33') doubled their lead rather against the run of play, Jervel Youngs challenged Jake Bloom for the ball from a long range free-kick before finding the unguarded net.
Wakeling (35') floated a dangerous right wing cross towards goal, which was tipped away crucially, before a big stop (36') thwarted Hadleigh at close range.
Bloom (39') held onto Youngs' header from Dennet's left wing free-kick, as Needham halved the deficit moments later.
A right wing cross picked out James Coton arriving at the far post to wrap home into the bottom far corner from an acute angle.
Needham (41') saw a close range header following a right wing cross seemingly tipped over, but for a goal-kick to be given, as Bloom (42') held onto a low tame strike at his left-hand post.
Evan Gledhill (45') was denied by a sharp save from the keeper, again turned passed his man on the right-hand side before dinking a great strike towards the top far corner only for the keeper to tip it onto the inside of the post to bounce back into his grateful gloves.
Gledhill (45'+2') spun into space only to fire narrowly over from inside the box to end the first half.
Wakeling (52') exploited space, albeit shooting low and straight at Bell at his near post, as Gledhill (54') curled a free-kick from just outside the box narrowly over.
Bloom (63') meanwhile was forced into an incredible stop, launching low to his right-hand side to tip a thunderous volley behind, as two crucial blocks a minute later, one from Drake at close range, denied Hadleigh from the resulting corner.
Coton (68') rifled Needham level. After Gledhill, Wakeling and Smy - the duo playing a smart one-two - linked up nicely, Coton was threaded through down the right-hand side by the forward to lash home into the bottom far corner.
Bobby's (71') good left wing free-kick was met by Fiddy leaping highest at the far post whose header was held by Bell, as Bobby (74') headed Needham in front.
Henry Vieira's great right wing cross was headed in off the underside of the crossbar by Flynn Bobby at close range to give Luke Betts' side a 3-2 lead.
Wakeling (76') fired straight at Bell, while Bobby's cross-shot was held by the keeper (79').
Gledhill (80') saw a low shot from a tight angle held by Bell, as Needham smashed narrowly over (81').
Fletch Stalford (83') fired over from outside the penalty area, as Hopkins' (85') far post header was headed off the line from Bobby's left wing corner as appeals for a penalty wwere waved away.
Needham remained on top, Henry Vieira (87') darted through onto the left-hand only for his low cutback to be turned behind for a corner, which was nodded wide of the far post by Drake.
Gledhill intercepted Bell's clearance (89'), though the stopper recovered to dive and gather the ball before it could trickle over his goal-line.
Bloom (91') advanced to claim a long range free-kick.
Needham:- 1 Jake Bloom, 2 Brad Smith, 3 Tyler Wright, 4 Kellen Fiddy (C), 5 Xavi Drake, 6 Charlie Smy, 7 Flynn Bobby, 8 Harry Hopkins, 10 James Coton (73' Vieira), 14 Oscar Wakeling, 19 Evan Gledhill. Subs: 9 Henry Vieira, 15 Kyle Roper, 16 Riley Parker, 17 Alfie Mark. 88' Smy & Bobby off for Parker and Mark.
Hadleigh:- 1 Josh Bell, 2 Alex Spraggons, 3 Theo Stalford, 4 Zach Simpson, 5 Alfie Tynan (C), 6 Luke Hyde, 7 Hasim Koksal, 8 Riley Dennet, 9 Jervel Youngs, 10 Rico Aubrey, 11 Jim Gregory. Subs: 12 Fletch Stalford, 14 Daniel Senah, 15 Charlie Smith, 16 Tyce Aubrey, 21 Oli Rose.
Booked: H GK (44'), Bobby (79')
Goals: James Coton (39', 68'), Flynn Bobby (74'); Dennet (8'), Youngs (33')


