The crowd at Layer Road were cheering with delight at half-time after Kevin Watson, Wayne Andrews and Craig Fagan had fired them into a 3-0 first-half lead.
However, at the end of the 90 minutes, they can be forgiven for their collective sighs of relief when the referee blew his final whistle after four extra mintues of stoppage time.
The first half had it all.
Working from the back there was Aidan Davison again in fine form, looking solid and coping with what finally got through to him.
The centre of defence was solid with Liam Chilvers and Wayne Brown standing firm and repelling anything that was hurled at them.
The wings provided plenty of openings and in the middle there was Watson and Bobby Bowry tackling hard and playing some creative passes to feet.
Up front, Fagan and Andrews terrorised the defence.
It was no surprise when the U's took the lead.
Watson's pile-driver of a first-time effort came after a long spell of possession.
It knocked any wind out of the Hatters' sails and Andrews capitalised on the half-hour mark.
Fagan made space for himself on the left and crossed low into Andrews.
The striker fluffed his first attempt, but the County defence had gone missing and allowed him all the time and space he needed to reclaim the ball and slot in the second.
Fagan was keen to get his name on the scoresheet and he benefitted from a lack of composure from the visitors.
Sam Stockley was fouled by Hatters' captain Mark Robertson on 41 minutes.
The free-kick was delievered by Watson and rising unchallenged to head home was Fagan.
However, in the second half Stockport came out fired up and the U's, it seemed, were not able to cope with this.
Andy Welsh came on and moments later Stockport pulled one back through Lee Cartwright.
Luke Beckett made things tense by bagging the 100th goal of his career with a deft header at the near post from Welsh's corner.
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