The Australian's 39, his team's top score, was an integral part of Colne's 165 as they battled against some accurate bowling.
With Harper in superb form with the bat, Nelson felt they had a chance but couldn't find anyone to stay with him.
The West Indies star was finally last man out for a remarkable 86 of Nelson's total of 130. His innings included five sixes and he was caught going for another big hit trying to rescue a lost cause.
Wickets were shared by the Colne bowlers and Nick Moulding - 2-11 from his 10 overs - turned in a superb spell.
Ramsbottom's reward for their four wicket win at Todmorden is a tough trip to East Lancashire in the semi-finals.
However, they will be confident if professional Ian Harvey can occupy the crease for any length of time as another quick-fire knock did much to overcome Todmorden's total of 143-9.
On a firm but green pitch, Todmorden professional Vasbert Drakes was a real handful with a hostile spell which brought him 3-29. He removed Harvey who miscued a pull to mid-on for 38 from 32 balls but by then Ramsbottom had reached 88. And despite losing three more wickets and playing and missing frequently they eased home with crucial runs from Mike Dentith and skipper Ian Bell.
The Ramsbottom attack shared the wickets around as Drakes and Stewart Priestley top scored for the hosts with 31.
East Lancs booked their place after a superb team effort in the field restricted Bacup to 109 at Alexandra Meadows. Professional Brad Young opened up with six successive maidens as the Blackburn side turned the screw from the off and he eventually conceded just six runs from his 10 overs.
That allowed Nasir Iqbal (2-9) and Phil Mooney (4-14) to capitalise from his pressure as the visitors were eventually dismissed in the final over setting 110 for victory.
John Chapman top scored with 25.
In reply, East Lancs slipped to 56-3 before skipper Mark Lomas was joined at the wicket by Phil Mercer.
They steered their side home with 17 overs to spare, putting on 57 for the fourth wicket, as Lomas lead the way with a fine unbeaten 71 off just 81 balls.
Mott shattered as Lowerhouse are dumped out
Worsley Cup: Lowerhouse 133, Haslingden 179
'SHATTERED' was the word Lowerhouse professional Matthew Mott used to describe his disappointment after holders Haslingden dumped his side out of this year's Worsley Cup.
Just four weeks earlier only the front windows of houses bordering the Liverpool Road ground were in danger of being shattered as Mott took apart the Haslingden attack on his way to a match-winning Lancashire League ton.
But his face had a glazed look when Stuart Taylor brought an end to his painstaking 43 on Saturday - a dismissal which all but brought the shutters down on Lowerhouse's hopes of a semi final spot.
The outlook had seemed a whole lot brighter for Mott and his team mates earlier in the day when they managed to skittle Haslingden for 179 after the visitors had got off to a flying start.
The Bentgate men looked well set for a big score as opener Jack Simpson laid the foundations with an 85-ball 42.
He shared stands of 60 with Mike Ingham (27) and 40 with Stuart Taylor (19) before Hamish Anthony arrived at the middle to add his own brand of magic.
The West Indian launched two towering sixes into orbit as the pair posted a quickfire 28 before Simpson was finally fourth man out with the score on 142.
And when Anthony's exhilarating 18-ball 24 came to an end just four more runs later, as Jez Hope claimed his first victim of a productive spell, it triggered a collapse. A mix up between Charles Lord and Mark Griffin lead to the Haslingden skipper being run out for three.
And Hope snapped up three more wickets as the tail could only muster 20 more runs before finally caving in on 179, with three overs and a ball still remaining.
Lowerhouse sensed their chance but their script was soon in tatters when a direct hit from Lord at short mid-wicket ran out Nicky Hope just three balls into their reply.
Mott then nicked a hostile delivery from Anthony but Paul Blackledge put down a sharp chance at first slip.
That fired the West Indian up and in his next over he sent Chris Bleazard's middle stump cartwheeling down the pitch.
He repeated the feat in the same over to remove Mark Whelan before he had time to trouble the scorers as Lowerhouse slumped to 15-3.
The runs dried up after that as Mott set about fighting the fire but the damage had been done.
Stan Heaton (14), Gary Moorhouse (six) and Matt Hope (nought) all came and went as Lowerhouse crawled to 74-6. A seventh wicket stand of 41 between Mott and Frank Entwistle momentarily revived the home fans hope.
But Mott's 107-ball resistance finally came to an end when Taylor slipped one through his defences in the 41st over.
Taylor then completely extinguished Lowerhouse's fading hopes when Entwistle was stumped after he had been tempted down the track.
Anthony and Taylor mopped up the last two wickets with the minimum of fuss to complete what turned out to be a comprehensive 46-run victory.
``We are shattered really because we had done all the hard work in restricting them to 179,'' said Mott.
``But as it turned out the wicket was seaming all day and once they got those three early wickets it became a battle for survival.
``We tried to rebuild but I got out the over before I was going to try and start to get in amongst them.
``So we missed out on some fun at the end but that's the way it goes I suppose.''