So... I have an explanation now! Here we go.
The purpose of the video in question was to help promote the channel, so as well as making the video I saw youtube's 'promote' button and went for it. Simple, right? I set a £2 budget expecting up to 100-ish views which was reasonable to get the word out a little more, nothing wrong with a little self promotion.
Now let's be clear, at the time of the spike my adwords account said the ad was 'under review', so inactive, hence the panic. Except it WAS actually live, and it stayed live well past my budget. It didn't stop until hitting 24k views, at a cost of £1,180
just a little more than my £2 budget.
Adwords updated overnight, so I woke up this morning to see £1.18k on my account. Explaining the spike, but creating a whole new issue.
Having spoken to Google, the charges above my budget are waived because they over-delivered. So for £2 I extended my reach to 24k viewers, some of which went on to watch my other videos, and gained 70 subs.
Now thats all cleared up, on to the bad stuff. From everyone elses point of view, having 24k on just one video seems suspect right? So much so I'm debating removing the video. I legitimately promoted my channel, but to others it probably looks like I bought views from some sketchy site.
What does everyone here think? I'm not the only one to have promoted in this way, guess I was just unlucky (or lucky?) to be the one Google screwed up on.