Ian,
I got a chance to watch your video! It was very fun and watchable. You are brave for putting this up for viewing!
There were a some pretty serious brewing NO-NOs in it however. :-( I am wondering about editing it a bit to correct them.
The big one was your sanitation protocal was okay for your bottles, but missing all together or lax in others. Your siphon was not sanitized, your corks, while boiled, were touched by hands (some multiple times!) during the corking procedure (and once by mouth - eek).
Another big one was pouring back into the main carboy. Anything removed from the carboy could have been infected, by pouring back the main carboy will be also infected.
A couple of suggestions to help your brewing:
StarSan is a quick and effective santizer. It is not expensive (it is sold as a concentrate and then home diluted). Put it in a spray bottle and wet any surface for 30 seconds to sanitize. Drain excess DO NOT RINSE and use. Don't worry about bubbles, they don't affect the taste. Sanitize your siphon, bottles, corks, hands, counters, etc. It is better to over-sanitize than to risk infection.
Siphon - use water to pull a siphon. The mouth is not sanitary! Pour water into the hose and have a container next to your first bottle. Drop the tip into the container until the color changes, then pinch off the siphon hose and bottle away. Sanitize the tip frequently especially if it is touched or touches other surfaces.
Or better - invest just a few more dollars for an auto-siphon and bottling wand.
I am not familiar with the corker you used or the process of boiling corks. I use a floor corker and only dip the end of the cork in StarSan. I've never lost a bottle. Well, okay, one bottle, but it refermented and the pressure blew the cork and mead aaaalllll over everything. In any case, let your bottles sit upright for 3 or so days to let the excess pressure escape, then turn your bottles. There is a recommended fill level which I am forgetting right now, I always look it up right prior to bottling. I *think* it is 1 inch below the bottom of the cork. Mentors?
One more thing, always handle your hydometer by the bulb. The are prone to snapping off if you hold them by the thin top.
I look forward to your next video! I'd suggest checking in with the Mead Mentors prior to your next one for technical brewing help on your project.
Again, thanks for the work you did!
All the best,
Leonora