After Evans was blocked in the area, Flynn seized on the loose ball to fire low past Scott Flinders in the 12th minute.
Porter doubled the hosts' advantage 11 minutes before half-time with a close-range header after Evans (pictured) back-heeled into the path of Flynn, who crossed from the left byline.
Peter Hartley grabbed a consolation for the visitors in stoppage time with a low shot.
Batth, the 21-year-old defender who has extended his stay from Wolves until the end of the season, headed in Chris Lines' cross after a short corner caught the struggling Lilywhites napping after four minutes.
Marshall, who Owls boss Gary Megson wanted to sign permanently before he agreed a new deal with Stoke, then added a second for Wednesday, while Jamie Douglas and Paul Parry wasted second-half chances for Preston.
MK Dons had to settle for a point away at Griffin Park after they drew 3-3 with Brentford, despite having assumed a three-goal lead.
The visitors scored twice in the opening six minutes through Darren Potter and Angelo Balanta, and Charlie MacDonald gave them a third before half-time in what seemed a convincing advantage.
But the hosts staged a remarkable recovery with a brace from Gary Alexander, and a stoppage-time equaliser from Leon Legge salvaged an improbable point.
Stevenage's promotion push took another positive step after a 1-0 victory against Wycombe Wanderers at Adams Park.
Midfielder Lawrie Wilson clinched the game's only goal as the visitors grabbed the winner with just seven minutes left in the match.
Colchester saw off 10-man Exeter 2-0 to finish 2011 on a high. The hosts early dominance paid off when they went ahead after 16 minutes through Wordsworth, who confidently swept home a low shot from the edge of the area from Henderson's pass, after Andy Bond had pounced on Troy Archibald-Henville's error.
Bond doubled Colchester's lead just after the hour with a fine finish from 15 yards, following Steven Gillespie's run and pass.
Oldham dealt Notts County a set back with a 3-2 victory in their clash at Boundary Park in what was a thrilling encounter.
Lee Hughes put County in front in just the 10th minute, but Luca Scapuzzi levelled the scores just before the half hour mark.
Neal Bishop restored the visitors' lead, but goals from Filipe Morais and Alex Diamond ensured that Oldham grabbed all three points.
Bournemouth continued their push towards the play-offs with a convincing 3-1 victory at Yeovil. Steven Gregory set the pattern with an excellent goal for the Cherries after six minutes.
The visitors doubled their lead after 26 minutes when Yeovil failed to cure a Marc Pugh corner and Wes Fogden was left unchallenged to score from close range.
Yeovil's Bondz N'Gala crashed a header against the bar just before half time but the visitors then reduced the arrears after 66 minutes when skipper Paul Huntington moved up from the back to head home Gavin Williams' right-wing corner.
However, Bournemouth deservedly had the last word when full-back Charlie Daniels embarked on a mazy dribble from the back and fired home from an angle, leaving defenders trailing in his wake.
Relegation-threatened teams Walsall and Rochdale had to settle for a point apiece following their goalless draw in a lively match at the Banks's Stadium.
An equaliser two minutes into stoppage time from midfielder Jimmy Ryan salvaged a 2-2 draw for struggling Scunthorpe against basement boys Chesterfield.