That video is ludicicrous. If rigging had gone on, the place to do it would have been the postal vote stage, not right out in the open before cameras.
1. The first lady swapping votes between Yes and No looks like she is trying to work out where to put a small number of ballots - the small number probably relates to the fact that they are 'spoiled' in some way - perhaps a mark that crosses both boxes, a comment written in a box, or something that makes the counters uncertain. These uncertain votes are usually taken up with the agents for the respective sides before being put into the final vote tally or disregarded.
2. The Sky News clip was probably not showing counted votes. The reference to turnout at the bottom of the screen suggests that it was early in the evening when votes were being verified. Verified means opening the ballot boxes and simply counting the number of ballots in order to determine how many there are. This is an important number for many reasons, not least to ensure that when all the votes are counted - yes, no, spoiled, the totals tally. The verified votes are put into bundles of hundreds and twenty-fives before they are actually counted.
3. There is no evidence that the man in the third clip is filling in a ballot paper. If he is, he is pretty lacksadaisical considering that more than 3.5 million votes were cast.
When counting/verifying takes place there are scrutineers from both sides who are allowed to stand over the counters checking that things are going properly.
Finally, you can usually tell a vote rigging op by the slow speed of things - eg, it taking a week to count votes in the Republican presidential primaries in 2012 (when Ron Paul seriously underperformed) or, more close to home, the fact that it took so long to count the votes in the London Borough of Tower Hamlets last May. Votes cast for councillors on the Thursday were still not counted by the following Monday. The media only sat up and took notice when it affected the Euro-count.