The important thing with a head lock before anything else, is to prevent the person from striking you, through interception, position, speed,etc. The later has the caveat that even if the person is not grounded or competent, when the strike comes it doesn't mean it won't do damage. Your reaction time will be affected by how much work you are doing. So even if you are normally super fast, it might be the stupidest mistake you have made not to deal with the incoming attack focusing too much on end game. On the other hand you don't wan to stick around.
In fact is there is no such thing as a "head lock", every situation is different. One thing I have learnt from martial arts is to get out of set mode, there are no set scenarios.
Having said that for side holds to the head you want to try to prevent the person putting you in the low position, by rearing up arching your back. This will make you less vulnerable and you can find a better position . Generally speaking the strategy is based on how how low down the person has got you you.
The standard roll (not the sit and roll) is quite a common one for low position, it is kind of a committed technique though. For part of the time you will have that person's weight on top of you as you are pulling them over. Consider if someone is twice you weight if you do get them to move, the weight is going to be comig down on top of you. You can do it with people heaver than you so long as you complete. However there are limits. So the sit and roll is a lot better.
There are so many techniques you can use. I guess I would choose "step to the side" due to simplicity. This is a high position technique. So you have 'reared up', ideally circle your leg behind so you you are mostly behind them,try and feed your hand inside around to put pressure on their neck (I like to strike under their jaw and poke fingers in the eyes) at the same time scoop their leg or grab material by the knee and lift, then just step sideways parallel to them, they have no where to go but down. If they haven't let go you can follow on much like they have done in the video.